# Frequently Asked Questions for FreeBSD 8.`X`, and 9.`X`

### The FreeBSD Documentation Project

Copyright © 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 The FreeBSD Documentation Project

This is the FAQ for FreeBSD versions 8.`X` and 9.`X`. Every effort has been made to make this FAQ as informative as possible; if you have any suggestions as to how it may be improved, please feel free to mail them to the FreeBSD documentation project mailing list.

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[ Split HTML / Single HTML ]

List of Tables
3-1. Maximum File Sizes

List of Examples
10-1. “InputDevice” Section for Wheeled Mouse in Xorg Configuration File
10-2. “.emacs” Example for Naive Page Scrolling with Wheeled Mouse (optional)

# Chapter 1 Introduction

1.1. What is FreeBSD?
1.2. What is the goal of the FreeBSD Project?
1.3. Does the FreeBSD license have any restrictions?
1.4. Can FreeBSD replace my current operating system?
1.5. Why is it called FreeBSD?
1.6. What are the differences between FreeBSD and NetBSD, OpenBSD, and other open source BSD operating systems?
1.7. What is the latest version of FreeBSD?
1.8. What is FreeBSD-CURRENT?
1.9. What is the FreeBSD-STABLE concept?
1.10. When are FreeBSD releases made?
1.11. Who is responsible for FreeBSD?
1.12. Where can I get FreeBSD?
1.13. How do I access the Problem Report database?

1.1. What is FreeBSD?

FreeBSD is a modern operating system for desktops, laptops, servers, and embedded systems with support for a large number of platforms.

It is based on U.C. Berkeley's “4.4BSD-Lite” release, with some “4.4BSD-Lite2” enhancements. It is also based indirectly on William Jolitz's port of U.C. Berkeley's “Net/2” to the i386™, known as “386BSD”, though very little of the 386BSD code remains.

FreeBSD is used by companies, Internet Service Providers, researchers, computer professionals, students and home users all over the world in their work, education and recreation.

For more detailed information on FreeBSD, please see the FreeBSD Handbook.

1.2. What is the goal of the FreeBSD Project?

The goal of the FreeBSD Project is to provide a stable and fast general purpose operating system that may be used for any purpose without strings attached.

1.3. Does the FreeBSD license have any restrictions?

Yes. Those restrictions do not control how you use the code, merely how you treat the FreeBSD Project itself. If you have serious license concerns, read the actual license. For the simply curious, the license can be summarized like this.

- Do not claim that you wrote this.

- Do not sue us if it breaks.

- Do not remove or modify the license.

Many of us have a significant investment in the project and would certainly not mind a little financial compensation now and then, but we definitely do not insist on it. We believe that our first and foremost “mission” is to provide code to any and all comers, and for whatever purpose, so that the code gets the widest possible use and provides the widest possible benefit. This, we believe, is one of the most fundamental goals of Free Software and one that we enthusiastically support.

Code in our source tree which falls under the GNU General Public License (GPL) or GNU Library General Public License (LGPL) comes with slightly more strings attached, though at least on the side of enforced access rather than the usual opposite. Due to the additional complexities that can evolve in the commercial use of GPL software, we do, however, endeavor to replace such software with submissions under the more relaxed FreeBSD license whenever possible.

1.4. Can FreeBSD replace my current operating system?

For most people, yes. But this question is not quite that cut-and-dried.

Most people do not actually use an operating system. They use applications. The applications are what really use the operating system. FreeBSD is designed to provide a robust and full-featured environment for applications. It supports a wide variety of web browsers, office suites, email readers, graphics programs, programming environments, network servers, and just about everything else you might want. Most of these applications can be managed through the Ports Collection.

If you need to use an application that is only available on one operating system, you simply cannot replace that operating system. Chances are there is a very similar application on FreeBSD, however. If you want a solid office or Internet server, a reliable workstation, or just the ability to do your job without interruptions, FreeBSD will almost certainly do everything you need. Many computer users across the world, including both novices and experienced UNIX® administrators, use FreeBSD as their only desktop operating system.

If you are migrating to FreeBSD from some other UNIX environment, you already know most of what you need to. If your background is in graphic-driven operating systems such as Windows® and Mac OS®, you may be interested in using PC-BSD, a FreeBSD based distribution, instead. If you have not used UNIX before expect to invest additional time learning the UNIX way of doing things. This FAQ and the FreeBSD Handbook are excellent places to start.

1.5. Why is it called FreeBSD?

- It may be used free of charge, even by commercial users.

- Full source for the operating system is freely available, and the minimum possible restrictions have been placed upon its use, distribution and incorporation into other work (commercial or non-commercial).

- Anyone who has an improvement or bug fix is free to submit their code and have it added to the source tree (subject to one or two obvious provisions).

- It is worth pointing out that the word “free” is being used in two ways here, one meaning “at no cost”, the other meaning “you can do whatever you like”. Apart from one or two things you cannot do with the FreeBSD code, for example pretending you wrote it, you can really do whatever you like with it.

1.6. What are the differences between FreeBSD and NetBSD, OpenBSD, and other open source BSD operating systems?

James Howard wrote a good explanation of the history and differences between the various projects, called The BSD Family Tree which goes a fair way to answering this question. Some of the information is out of date, but the history portion in particular remains accurate.

Most of the BSDs share patches and code, even today. All of the BSDs have common ancestry.

The design goals of FreeBSD are described in Q: 1.2., above. The design goals of the other most popular BSDs may be summarized as follows:

- OpenBSD aims for operating system security above all else. The OpenBSD team wrote ssh(1) and pf(4), which have both been ported to FreeBSD.

- NetBSD aims to be easily ported to other hardware platforms.

- DragonFly BSD is a fork of FreeBSD 4.8 that has since developed many interesting features of its own, including the HAMMER file system and support for user-mode “vkernels”.

1.7. What is the latest version of FreeBSD?

At any point in the development of FreeBSD, there can be multiple parallel branches. 9.`X` releases are made from the 9-STABLE branch, and 8.`X` releases are made from the 8-STABLE branch.

Up until the release of 9.0, the 8.`X` series was the one known as -STABLE. However, as of 10.`X`, the 8.`X`. branch will be designated for an “extended support” status and receive only fixes for major problems, such as security-related fixes.

Version 9.1 is the latest release from the 9-STABLE branch; it was released in December 2012. Version 8.4 is the latest release from the 8-STABLE branch; it was released in April 2013.

Briefly, -STABLE is aimed at the ISP, corporate user, or any user who wants stability and a minimal number of changes compared to the new (and possibly unstable) features of the latest -CURRENT snapshot. Releases can come from either branch, but -CURRENT should only be used if you are prepared for its increased volatility (relative to -STABLE, that is).

Releases are made every few months. While many people stay more up-to-date with the FreeBSD sources (see the questions on FreeBSD-CURRENT and FreeBSD-STABLE) than that, doing so is more of a commitment, as the sources are a moving target.

More information on FreeBSD releases can be found on the Release Engineering page on the FreeBSD Web site.

1.8. What is FreeBSD-CURRENT?

FreeBSD-CURRENT is the development version of the operating system, which will in due course become the new FreeBSD-STABLE branch. As such, it is really only of interest to developers working on the system and die-hard hobbyists. See the relevant section in the Handbook for details on running -CURRENT.

If you are not familiar with FreeBSD you should not use FreeBSD-CURRENT. This branch sometimes evolves quite quickly and due to mistake can be un-buildable at times. People that use FreeBSD-CURRENT are expected to be able to analyze, debug, and report problems.

FreeBSD snapshot releases are made based on the current state of the -CURRENT and -STABLE branches. The goals behind each snapshot release are:

- To test the latest version of the installation software.

- To give people who would like to run -CURRENT or -STABLE but who do not have the time or bandwidth to follow it on a day-to-day basis an easy way of bootstrapping it onto their systems.

- To preserve a fixed reference point for the code in question, just in case we break something really badly later. (Although Subversion normally prevents anything horrible like this happening.)

- To ensure that all new features and fixes in need of testing have the greatest possible number of potential testers.

No claims are made that any -CURRENT snapshot can be considered “production quality” for any purpose. If you want to run a stable and fully tested system, you will have to stick to full releases, or use the -STABLE snapshots.

Snapshot releases are directly available from snapshot.

Official snapshots are generated on a regular basis for all actively developed branches.

1.9. What is the FreeBSD-STABLE concept?

Back when FreeBSD 2.0.5 was released, FreeBSD development branched in two. One branch was named -STABLE, one -CURRENT. FreeBSD-STABLE is intended for Internet Service Providers and other commercial enterprises for whom sudden shifts or experimental features are quite undesirable. It receives only well-tested bug fixes and other small incremental enhancements. FreeBSD-CURRENT, on the other hand, has been one unbroken line since 2.0 was released, leading towards 9.1-RELEASE and beyond. For more detailed information on branches see “FreeBSD Release Engineering: Creating the Release Branch”, the status of the branches and the upcoming release schedule can be found on the Release Engineering Information page.

9.1-STABLE is the actively developed -STABLE branch. The latest release on the 9.1-STABLE branch is 9.1-RELEASE, which was released in December 2012.

The 10-CURRENT branch is the actively developed -CURRENT branch toward the next generation of FreeBSD. See What is FreeBSD-CURRENT? for more information on this branch.

1.10. When are FreeBSD releases made?

The Release Engineering Team `<re@FreeBSD.org>` releases a new major version of FreeBSD about every 18 months and a new minor version about every 8 months, on average. Release dates are announced well in advance, so that the people working on the system know when their projects need to be finished and tested. A testing period precedes each release, to ensure that the addition of new features does not compromise the stability of the release. Many users regard this caution as one of the best things about FreeBSD, even though waiting for all the latest goodies to reach -STABLE can be a little frustrating.

More information on the release engineering process (including a schedule of upcoming releases) can be found on the release engineering pages on the FreeBSD Web site.

For people who need or want a little more excitement, binary snapshots are made daily as discussed above.

1.11. Who is responsible for FreeBSD?

The key decisions concerning the FreeBSD project, such as the overall direction of the project and who is allowed to add code to the source tree, are made by a core team of 9 people. There is a much larger team of more than 350 committers who are authorized to make changes directly to the FreeBSD source tree.

However, most non-trivial changes are discussed in advance in the mailing lists, and there are no restrictions on who may take part in the discussion.

1.12. Where can I get FreeBSD?

Every significant release of FreeBSD is available via anonymous FTP from the FreeBSD FTP site:

- The latest 9-STABLE release, 9.1-RELEASE can be found in the 9.1-RELEASE directory.

- Snapshot releases are made monthly for the -CURRENT and -STABLE branch, these being of service purely to bleeding-edge testers and developers.

- The latest 8-STABLE release, 8.4-RELEASE can be found in the 8.4-RELEASE directory.

Information about obtaining FreeBSD on CD, DVD, and other media can be found in the Handbook.

1.13. How do I access the Problem Report database?

The Problem Report database of all user change requests may be queried by using our web-based PR query interface.

The send-pr(1) command can be used to submit problem reports and change requests via electronic mail. Alternatively, the web-based problem report submission interface can be used to submit problem reports through a web browser.

Before submitting a problem report, please read Writing FreeBSD Problem Reports, an article on how to write good problem reports.

# Chapter 2 Documentation and Support

2.1. What good books are there about FreeBSD?
2.2. Is the documentation available in other formats, such as plain text (ASCII), or PostScript®?
2.3. Where do I find info on the FreeBSD mailing lists? What FreeBSD news groups are available?
2.4. Are there FreeBSD IRC (Internet Relay Chat) channels?
2.5. Are there any web based forums to discuss FreeBSD?
2.6. Where can I get commercial FreeBSD training and support?

2.1. What good books are there about FreeBSD?

The project produces a wide range of documentation, available online from this link: http://www.FreeBSD.org/docs.html. In addition, the Bibliography at the end of this FAQ, and the one in the Handbook reference other recommended books.

2.2. Is the documentation available in other formats, such as plain text (ASCII), or PostScript®?

Yes. The documentation is available in a number of different formats and compression schemes on the FreeBSD FTP site, in the /pub/FreeBSD/doc/ directory.

The documentation is categorized in a number of different ways. These include:

- The document's name, such as `faq`, or `handbook`.

- The document's language and encoding. These are based on the locale names you will find under `/usr/share/locale` on your FreeBSD system. The current languages and encodings that we have for documentation are as follows:

  Name | Meaning
  --- | ---
  `en_US.ISO8859-1` | English (United States)
  `bn_BD.ISO10646-1` | Bengali or Bangla (Bangladesh)
  `da_DK.ISO8859-1` | Danish (Denmark)
  `de_DE.ISO8859-1` | German (Germany)
  `el_GR.ISO8859-7` | Greek (Greece)
  `es_ES.ISO8859-1` | Spanish (Spain)
  `fr_FR.ISO8859-1` | French (France)
  `hu_HU.ISO8859-2` | Hungarian (Hungary)
  `it_IT.ISO8859-15` | Italian (Italy)
  `ja_JP.eucJP` | Japanese (Japan, EUC encoding)
  `mn_MN.UTF-8` | Mongolian (Mongolia, UTF-8 encoding)
  `nl_NL.ISO8859-1` | Dutch (Netherlands)
  `no_NO.ISO8859-1` | Norwegian (Norway)
  `pl_PL.ISO8859-2` | Polish (Poland)
  `pt_BR.ISO8859-1` | Portuguese (Brazil)
  `ru_RU.KOI8-R` | Russian (Russia, KOI8-R encoding)
  `sr_YU.ISO8859-2` | Serbian (Serbia)
  `tr_TR.ISO8859-9` | Turkish (Turkey)
  `zh_CN.GB2312` | Simplified Chinese (China, GB2312 encoding)
  `zh_TW.Big5` | Traditional Chinese (Taiwan, Big5 encoding)

  > Note: Some documents may not be available in all languages.

- The document's format. We produce the documentation in a number of different output formats. Each format has its own advantages and disadvantages. Some formats are better suited for online reading, while others are meant to be aesthetically pleasing when printed on paper. Having the documentation available in any of these formats ensures that our readers will be able to read the parts they are interested in, either on their monitor, or on paper after printing the documents. The currently available formats are:

  Format | Meaning
  --- | ---
  `html-split` | A collection of small, linked, HTML files.
  `html` | One large HTML file containing the entire document
  `pdf` | Adobe's Portable Document Format
  `ps` | PostScript
  `rtf` | Microsoft's Rich Text Format
  `txt` | Plain text

  > Note: Page numbers are not automatically updated when loading Rich Text Format into Word. Press Ctrl+A, Ctrl+End, F9 after loading the document, to update the page numbers.

- The compression and packaging scheme.

  1. Where the format is `html-split`, the files are bundled up using tar(1). The resulting `.tar` file is then compressed using the compression schemes detailed in the next point.

  2. All the other formats generate one file, called ``type`.`format`` (i.e., `article.pdf`, `book.html`, and so on).

     These files are then compressed using either the `zip` or `bz2` compression schemes. tar(1) can be used to uncompress these files.

     So the PostScript version of the Handbook, compressed using `bzip2` will be stored in a file called `book.ps.bz2` in the `handbook/` directory.

After choosing the format and compression mechanism that you want to download, you will have to download the compressed files yourself, uncompress them, and then copy the appropriate documents into place.

For example, the split HTML version of the FAQ, compressed using bzip2(1), can be found in `doc/en_US.ISO8859-1/books/faq/book.html-split.tar.bz2` To download and uncompress that file you would have to do this:

    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/en_US.ISO8859-1/books/faq/book.html-split.tar.bz2
    # tar xvf book.html-split.tar.bz2

If the file is compressed, tar will automatically detect the appropriate format and decompress it correctly. You will be left with a collection of `.html` files. The main one is called `index.html`, which will contain the table of contents, introductory material, and links to the other parts of the document. You can then copy or move these to their final location as necessary.

2.3. Where do I find info on the FreeBSD mailing lists? What FreeBSD news groups are available?

You can find full information in the Handbook entry on mailing-lists and the Handbook entry on newsgroups.

2.4. Are there FreeBSD IRC (Internet Relay Chat) channels?

Yes, most major IRC networks host a FreeBSD chat channel:

- Channel `#FreeBSDhelp` on EFNet is a channel dedicated to helping FreeBSD users. They are much more sympathetic to questions than `#FreeBSD` is.

- Channel `##FreeBSD` on Freenode is a general help channel with many users at any time. The conversations have been known to run off-topic for a while, but priority is given to users with FreeBSD questions. We are good about helping you understand the basics, referring to the Handbook whenever possible, and directing you where to learn more about the topic you need help with. We are a primarily English speaking channel, though we have users from all over the world. If you would like to speak in your native language, try to ask the question in English and then relocate to another channel `##freebsd-`lang`` as appropriate.

- Channel `#FreeBSD` on DALNET is available at `irc.dal.net` in the US and `irc.eu.dal.net` in Europe.

- Channel `#FreeBSD` on UNDERNET is available at `us.undernet.org` in the US and `eu.undernet.org` in Europe. Since it is a help channel, be prepared to read the documents you are referred to.

- Channel `#FreeBSD` on RUSNET is a russian-language oriented channel dedicated to helping FreeBSD users. This is also good place for non-technical discussions.

- Channel `#bsdchat` on Freenode is a Traditional-Chinese (UTF-8 encoding) language oriented channel dedicated to helping FreeBSD users. This is also good place for non-technical discussions.

The FreeBSD wiki has a good list of IRC channels.

Each of these channels are distinct and are not connected to each other. Their chat styles also differ, so you may need to try each to find one suited to your chat style. As with all types of IRC traffic, if you are easily offended or cannot deal with lots of young people (and more than a few older ones) doing the verbal equivalent of jello wrestling, do not even bother with it.

2.5. Are there any web based forums to discuss FreeBSD?

The official FreeBSD forums are located at http://forums.FreeBSD.org/.

2.6. Where can I get commercial FreeBSD training and support?

iXsystems, Inc., parent company of the FreeBSD Mall, provides commercial FreeBSD and PC-BSD software support, in addition to FreeBSD development and tuning solutions.

BSD Certification Group, Inc. provides system administration certifications for DragonFly BSD, FreeBSD, NetBSD, OpenBSD. If you are interested in them, visit their site.

Any other organizations providing training and support should contact the Project to be listed here.

# Chapter 3 Installation

Nik Clayton

3.1. Which platform should I download? I have a 64 bit capable Intel® CPU, but I only see `amd64`.
3.2. Which file do I download to get FreeBSD?
3.3. What do I do if the images do not fit on a single disk?
3.4. Where are the instructions for installing FreeBSD?
3.5. What do I need to run FreeBSD?
3.6. How can I make my own custom release or install disk?
3.7. Can Windows co-exist with FreeBSD?
3.8. Another operating system destroyed my Boot Manager. How do I get it back?
3.9. I booted from my ATAPI CD-ROM, but the install program says no CD-ROM is found. Where did it go?
3.10. Do I need to install the source?
3.11. Do I need to build a kernel?
3.12. Should I use DES, Blowfish, or MD5 passwords and how do I specify which form my users receive?
3.13. What are the limits for memory?
3.14. What are the limits for FFS file systems?
3.15. Why do I get an error message, “`readin failed`” after compiling and booting a new kernel?
3.16. Is there a tool to perform post-installation configuration tasks?

3.1. Which platform should I download? I have a 64 bit capable Intel® CPU, but I only see `amd64`.

amd64 is the term FreeBSD uses for 64-bit compatible x86 architectures (also known as "x86-64" or "x64"). Most modern computers should use amd64. Older hardware should use i386. If you are installing on a non-x86-compatible architecture select the platform which best matches the architecture you are using.

3.2. Which file do I download to get FreeBSD?

On the Getting FreeBSD page select `[iso]` next to the architecture you want to use.

Any of the following can be used:

file | description
--- | ---
`disc1.iso` | Contains enough to install FreeBSD and a minimal set of packages.
`dvd1.iso` | Similar to `disc1.iso` but with additional packages.
`memstick.img` | A bootable image sufficient for writing to a USB stick.
`bootonly.iso` | A minimal image that requires network access during installation to completely install FreeBSD.

pc98 users require these floppy images: `floppies/boot.flp`, `floppies/kern1.flp`, `floppies/kern2.flp`, and `floppies/mfsroot1.flp`. These images need to be written onto floppies by tools like dd(1).

Full instructions on this procedure and a little bit more about installation issues in general can be found in the Handbook entry on installing FreeBSD.

3.3. What do I do if the images do not fit on a single disk?

Common mistakes when preparing the boot media are:

- Not downloading the image in binary mode when using FTP.

  Some FTP clients default their transfer mode to ascii and attempt to change any end-of-line characters received to match the conventions used by the client's system. This will almost invariably corrupt the boot image. Check the SHA-256 of the downloaded boot image: if it is not exactly that on the server, then the download process is suspect.

  To workaround: type binary at the FTP command prompt after getting connected to the server and before starting the download of the image.

- Using the DOS `copy` command (or equivalent GUI tool) to transfer the boot image to floppy.

  Programs like `copy` will not work as the boot image has been created to be booted into directly. The image has the complete content of the floppy, track for track, and is not meant to be placed on the floppy as a regular file. You have to transfer it to the floppy “raw”, using the low-level tools (e.g., `fdimage` or `rawrite`) described in the installation guide to FreeBSD.

3.4. Where are the instructions for installing FreeBSD?

Installation instructions for versions since FreeBSD 9.0 can be found at Handbook entry on installing FreeBSD. Older instructions can be found in the legacy entry on installing FreeBSD.

3.5. What do I need to run FreeBSD?

For FreeBSD you will need a 486 or better PC, with 64 MB or more of RAM and at least 1 GB of hard disk space.

See also Chapter 4.

3.6. How can I make my own custom release or install disk?

Customized FreeBSD installation media can be created by building a custom release. Follow the instructions in the Release Engineering article.

3.7. Can Windows co-exist with FreeBSD?

If Windows is installed first, then yes. FreeBSD's boot manager will then manage to boot Windows and FreeBSD. If you install Windows second, it will boorishly overwrite your boot manager without even asking. If that happens, see the next section.

3.8. Another operating system destroyed my Boot Manager. How do I get it back?

This depends on what boot manager you have installed. The FreeBSD boot selection menu (likely what you are using if you end up in this situation) can be reinstalled using boot0cfg(8). For example, to restore the boot menu onto the disk `ada0`:

    # boot0cfg -B ada0

The non-interactive MBR bootloader can be installed using gpart(8):

    # gpart bootcode -b /boot/mbr ada0

For more complex situations, including GPT disks, see gpart(8).

3.9. I booted from my ATAPI CD-ROM, but the install program says no CD-ROM is found. Where did it go?

The usual cause of this problem is a mis-configured CD-ROM drive. Many PCs now ship with the CD-ROM as the slave device on the secondary IDE controller, with no master device on that controller. This is illegal according to the ATAPI specification, but Windows plays fast and loose with the specification, and the BIOS ignores it when booting. This is why the BIOS was able to see the CD-ROM to boot from it, but why FreeBSD cannot see it to complete the install.

Reconfigure your system so that the CD-ROM is either the master device on the IDE controller it is attached to, or make sure that it is the slave on an IDE controller that also has a master device.

3.10. Do I need to install the source?

In general, no. There is nothing in the base system which requires the presence of the source to operate. Some ports, like `sysutils/lsof`, will not build unless the source is installed. In particular, if the port builds a kernel module or directly operates on kernel structures, the source must be installed.

3.11. Do I need to build a kernel?

Usually not. The supplied `GENERIC` kernel contains the drivers an ordinary computer will need. freebsd-update(8), the FreeBSD binary upgrade tool, cannot upgrade custom kernels, another reason to stick with the `GENERIC` kernel when possible. For computers with very limited RAM, such as embedded systems, it may be worthwhile to build a smaller custom kernel containing just the required drivers.

3.12. Should I use DES, Blowfish, or MD5 passwords and how do I specify which form my users receive?

FreeBSD 7 and 8 use MD5 password hashing by default. Recent versions of FreeBSD use SHA512 by default. These are believed to be more secure than the traditional UNIX password format, which used a scheme based on the DES algorithm. DES passwords are still available if you need to share your password file with legacy operating systems which still use the less secure password format. FreeBSD also allows you to use the Blowfish and MD5 password formats. Which password format to use for new passwords is controlled by the `passwd_format` login capability in `/etc/login.conf`, which takes values of `des`, `blf` (if these are available) or `md5`. See the login.conf(5) manual page for more information about login capabilities.

3.13. What are the limits for memory?

Memory limits depend on the platform used. On a standard i386 install, the limit is 4 GB but more memory can be supported through pae(4). See instructions for using 4 GB or more memory on i386.

FreeBSD/pc98 has a limit of 4 GB memory, and PAE can not be used with it. Other architectures supported by FreeBSD have much higher theoretical limits on maximum memory (many terabytes).

3.14. What are the limits for FFS file systems?

For FFS file systems, the maximum theoretical limit is 8 TB (2 G blocks), or 16 TB for the default block size of 8 KB. In practice, there is a soft limit of 1 TB, but with modifications file systems with 4 TB are possible (and exist).

The maximum size of a single FFS file is approximately 1 G blocks, or 4 TB with a block size of 4 KB.

Table 3-1. Maximum File Sizes

FS Block Size | Works | Should Work
--- | --- | ---
4 KB | > 4 GB | 4 TB - 1
8 KB | > 32 GB | 32 TB - 1
16 KB | > 128 GB | 32 TB - 1
32 KB | > 512 GB | 64 TB - 1
64 KB | > 2048 GB | 128 TB - 1

When the FS block size is 4 KB, triple indirect blocks work and everything should be limited by the maximum FS block number that can be represented using triple indirect blocks (approx. 10243 + 10242 + 1024), but everything is limited by a (wrong) limit of 1 G - 1 on FS block numbers. The limit on FS block numbers should be 2 G - 1. There are some bugs for FS block numbers near 2 G - 1, but such block numbers are unreachable when the FS block size is 4 KB.

For block sizes of 8 KB and larger, everything should be limited by the 2 G - 1 limit on FS block numbers, but is actually limited by the 1 G - 1 limit on FS block numbers. Using the correct limit of 2 G - 1 blocks does cause problems.

3.15. Why do I get an error message, “`readin failed`” after compiling and booting a new kernel?

Because your world and kernel are out of sync. This is not supported. Be sure you use `make `buildworld`` and `make `buildkernel`` to update your kernel.

You can boot by specifying the kernel directly at the second stage, pressing any key when the `|` shows up before loader is started.

3.16. Is there a tool to perform post-installation configuration tasks?

Yes, `HEAD` users can set `WITH_BSDCONFIG` in `/etc/src.conf`. Users of 9.`X` and higher may also install `sysutils/bsdconfig`.

# Chapter 4 Hardware Compatibility

## 4.1 General

4.1.1. I want to get a piece of hardware for my FreeBSD system. Which model/brand/type is best?
4.1.2. Does FreeBSD support more than 4 GB of memory (RAM)? More than 16 GB? More than 48 GB?
4.1.3. Why does FreeBSD report less than 4 GB memory when installed on an i386 machine?

4.1.1. I want to get a piece of hardware for my FreeBSD system. Which model/brand/type is best?

This is discussed continually on the FreeBSD mailing lists. Since hardware changes so quickly, however, we expect this. We still strongly recommend that you read through the Hardware Notes for FreeBSD 9.1 or 8.4 and search the mailing list archives before asking about the latest and greatest hardware. Chances are a discussion about the type of hardware you are looking for took place just last week.

If you are looking for a laptop, check the FreeBSD laptop computer mailing list archives. Otherwise, you probably want the archives for the FreeBSD general questions mailing list, or possibly a specific mailing list for a particular hardware type.

4.1.2. Does FreeBSD support more than 4 GB of memory (RAM)? More than 16 GB? More than 48 GB?

Yes. FreeBSD as an operating system generally supports as much physical memory (RAM) as the platform it is running on does. Keep in mind that different platforms have different limits for memory; for example i386 without PAE supports at most 4 GB of memory (and usually less than that because of PCI address space) and i386 with PAE supports at most 64 GB memory. AMD64 platforms currently deployed support up to 1 TB of physical memory.

4.1.3. Why does FreeBSD report less than 4 GB memory when installed on an i386 machine?

The total address space on i386 machines is 32-bit, meaning that at most 4 GB of memory is addressable (can be accessed). Furthermore, some addresses in this range are reserved by hardware for different purposes, for example for using and controlling PCI devices, for accessing video memory, and so on. Therefore, the total amount of memory usable by the operating system for its kernel and applications is limited to significantly less than 4 GB. Usually, 3.2 GB to 3.7 GB is the maximum usable physical memory in this configuration.

To access more than 3.2 GB to 3.7 GB of installed memory (meaning up to 4 GB but also more than 4 GB), a special tweak called PAE must be used. PAE stands for Physical Address Extension and is a way for 32-bit x86 CPUs to address more than 4 GB of memory. It remaps the memory that would otherwise be overlaid by address reservations for hardware devices above the 4 GB range and uses it as additional physical memory (see pae(4)). Using PAE has some drawbacks; this mode of memory access is a little bit slower than the normal (without PAE) mode and loadable modules (see kld(4)) are not supported. This means all drivers must be compiled into the kernel.

The most common way to enable PAE is to build a new kernel with the special ready-provided kernel configuration file called `PAE`, which is already configured to build a safe kernel. Note that some entries in this kernel configuration file are too conservative and some drivers marked as unready to be used with PAE are actually usable. A rule of thumb is that if the driver is usable on 64-bit architectures (like AMD64), it is also usable with PAE. If you wish to create your own kernel configuration file, you can enable PAE by adding the following line to your configuration:

    options       PAE

PAE is not much used nowadays because most new x86 hardware also supports running in 64-bit mode, known as AMD64 or Intel 64. It has a much larger address space and does not need such tweaks. FreeBSD supports AMD64 and it is recommended that this version of FreeBSD be used instead of the i386 version if 4 GB or more memory is required.

## 4.2 Architectures and Processors

4.2.1. Does FreeBSD support architectures other than the x86?
4.2.2. Does FreeBSD support Symmetric Multiprocessing (SMP)?
4.2.3. What is microcode? How do I install Intel CPU microcode updates?

4.2.1. Does FreeBSD support architectures other than the x86?

Yes. FreeBSD divides support into multiple tiers. Tier 1 architectures, such as i386 or amd64; are fully supported. Tiers 2 and 3 are supported on an if-possible basis. A full explanation of the tier system is available in the Committer's Guide.

A complete list of supported architectures can be found on the platforms page.

4.2.2. Does FreeBSD support Symmetric Multiprocessing (SMP)?

Symmetric multi-processor (SMP) systems are generally supported by FreeBSD, although in some cases, BIOS or motherboard bugs may generate some problems.

FreeBSD will take advantage of HyperThreading (HTT) support on Intel CPUs that support this feature. A kernel with the `options SMP` option, enabled by default, will automatically detect the additional logical processors.

smp(4) has more details.

4.2.3. What is microcode? How do I install Intel CPU microcode updates?

Microcode is a method of programmatically implementating hardware level instructions. This allows for CPU bugs to be fixed without replacing the on board chip.

Install `sysutils/devcpu-data`, then add:

    microcode_update_enable="YES"

to `/etc/rc.conf`

## 4.3 Hard Drives, Tape Drives, and CD and DVD Drives

4.3.1. What kind of hard drives does FreeBSD support?
4.3.2. Which SCSI or SAS controllers are supported?
4.3.3. What types of tape drives are supported?
4.3.4. Does FreeBSD support tape changers?
4.3.5. Which CD-ROM drives are supported by FreeBSD?
4.3.6. Which CD-RW drives are supported by FreeBSD?

4.3.1. What kind of hard drives does FreeBSD support?

FreeBSD supports EIDE, SATA, SCSI, and SAS drives (with a compatible controller; see the next section), and all drives using the original “Western Digital” interface (MFM, RLL, ESDI, and of course IDE). A few ESDI controllers that use proprietary interfaces may not work: stick to WD1002/3/6/7 interfaces and clones.

4.3.2. Which SCSI or SAS controllers are supported?

See the complete list in the Hardware Notes for FreeBSD 9.1 or 8.4.

4.3.3. What types of tape drives are supported?

FreeBSD supports SCSI and QIC-36 (with a QIC-02 interface). This includes 8-mm (aka Exabyte) and DAT drives.

Some of the early 8-mm drives are not quite compatible with SCSI-2, and may not work well with FreeBSD.

4.3.4. Does FreeBSD support tape changers?

FreeBSD supports SCSI changers using the ch(4) device and the chio(1) command. The details of how you actually control the changer can be found in the chio(1) manual page.

If you are not using AMANDA or some other product that already understands changers, remember that they only know how to move a tape from one point to another, so you need to keep track of which slot a tape is in, and which slot the tape currently in the drive needs to go back to.

4.3.5. Which CD-ROM drives are supported by FreeBSD?

Any SCSI drive connected to a supported controller is supported. Most ATAPI compatible IDE CD-ROMs are supported.

4.3.6. Which CD-RW drives are supported by FreeBSD?

FreeBSD supports any ATAPI-compatible IDE CD-R or CD-RW drive. See burncd(8) for details.

FreeBSD also supports any SCSI CD-R or CD-RW drives. Install and use `cdrecord` from the ports or packages system, and make sure that you have the `pass` device compiled in your kernel.

## 4.4 Keyboards and Mice

4.4.1. Is it possible to use a mouse in any way outside the X Window system?
4.4.2. How do I cut and paste text with a mouse in the text console?
4.4.3. My mouse has a fancy wheel and buttons. Can I use them in FreeBSD?
4.4.4. How do I use my delete key in `sh` and `csh`?

4.4.1. Is it possible to use a mouse in any way outside the X Window system?

If you are using the default console driver, syscons(4), you can use a mouse pointer in text consoles to cut & paste text. Run the mouse daemon, moused(8), and turn on the mouse pointer in the virtual console:

    # moused -p /dev/xxxx -t yyyy
    # vidcontrol -m on

Where `xxxx` is the mouse device name and `yyyy` is a protocol type for the mouse. The mouse daemon can automatically determine the protocol type of most mice, except old serial mice. Specify the `auto` protocol to invoke automatic detection. If automatic detection does not work, see the moused(8) manual page for a list of supported protocol types.

If you have a PS/2 mouse, just add `moused_enable="YES"` to `/etc/rc.conf` to start the mouse daemon at boot-time. Additionally, if you would like to use the mouse daemon on all virtual terminals instead of just the console, add `allscreens_flags="-m on"` to `/etc/rc.conf`.

When the mouse daemon is running, access to the mouse must be coordinated between the mouse daemon and other programs such as X Windows. Refer to the FAQ Why does my mouse not work with X? for more details on this issue.

4.4.2. How do I cut and paste text with a mouse in the text console?

It is not possible to remove data using the mouse. However, it is possible to “copy and paste”. Once you get the mouse daemon running (see the previous question) hold down button 1 (left button) and move the mouse to select a region of text. Then, press button 2 (middle button) to paste it at the text cursor. Pressing button 3 (right button) will “extend” the selected region of text.

If your mouse does not have a middle button, you may wish to emulate one or remap buttons using mouse daemon options. See the moused(8) manual page for details.

4.4.3. My mouse has a fancy wheel and buttons. Can I use them in FreeBSD?

The answer is, unfortunately, “It depends”. These mice with additional features require specialized driver in most cases. Unless the mouse device driver or the user program has specific support for the mouse, it will act just like a standard two, or three button mouse.

For the possible usage of wheels in the X Window environment, refer to that section.

4.4.4. How do I use my delete key in `sh` and `csh`?

For the Bourne Shell, add the following lines to your `.shrc`. See sh(1) and editrc(5).

    bind ^? ed-delete-next-char # for console
    bind ^[[3~ ed-delete-next-char # for xterm

For the C Shell, add the following lines to your `.cshrc`. See csh(1).

    bindkey ^? delete-char # for console
    bindkey ^[[3~ delete-char # for xterm

For more information, see this page.

## 4.5 Other Hardware

4.5.1. Workarounds for no sound from my pcm(4) sound card?
4.5.2. Does FreeBSD support power management on my laptop?

4.5.1. Workarounds for no sound from my pcm(4) sound card?

Some sound cards set their output volume to 0 at every boot. Run the following command every time the machine boots:

    # mixer pcm 100 vol 100 cd 100

4.5.2. Does FreeBSD support power management on my laptop?

FreeBSD supports the ACPI features found in modern hardware. Further information can be found in acpi(4).

# Chapter 5 Troubleshooting

5.1. Why is FreeBSD finding the wrong amount of memory on i386 hardware?
5.2. Why do my programs occasionally die with “`Signal 11`” errors?
5.3. My system crashes with either “`Fatal trap 12: page fault in kernel mode`”, or “`panic:`”, and spits out a bunch of information. What should I do?
5.4. Why do I get the error “`maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5)`”?
5.5. Why does sendmail give me an error reading “`mail loops back to myself`”?
5.6. Why do full screen applications on remote machines misbehave?
5.7. Why does it take so long to connect to my computer via `ssh` or `telnet`?
5.8. Why does “`file: table is full`” show up repeatedly in dmesg(8)?
5.9. Why does the clock on my computer keep incorrect time?
5.10. What does the error “`swap_pager: indefinite wait buffer:`” mean?
5.11. What is a “`lock order reversal`”?
5.12. What does “`Called ... with the following non-sleepable locks held`” mean?
5.13. Why does `buildworld`/`installworld` die with the message “`touch: not found`”?

5.1. Why is FreeBSD finding the wrong amount of memory on i386 hardware?

The most likely reason is the difference between physical memory addresses and virtual addresses.

The convention for most PC hardware is to use the memory area between 3.5 GB and 4 GB for a special purpose (usually for PCI). This address space is used to access PCI hardware. As a result real, physical memory can not be accessed by that address space.

What happens to the memory that should appear in that location is dependent on your hardware. Unfortunately, some hardware does nothing and the ability to use that last 500 MB of RAM is entirely lost.

Luckily, most hardware remaps the memory to a higher location so that it can still be used. However, this can cause some confusion if you watch the boot messages.

On a 32-bit version of FreeBSD, the memory appears lost, since it will be remapped above 4 GB, which a 32-bit kernel is unable to access. In this case, the solution is to build a PAE enabled kernel. See the entry on memory limits and about different memory limits on different platforms for more information.

On a 64-bit version of FreeBSD, or when running a PAE-enabled kernel, FreeBSD will correctly detect and remap the memory so it is usable. During boot, however, it may seem as if FreeBSD is detecting more memory than the system really has, due to the described remapping. This is normal and the available memory will be corrected as the boot process completes.

5.2. Why do my programs occasionally die with “`Signal 11`” errors?

Signal 11 errors are caused when your process has attempted to access memory which the operating system has not granted it access to. If something like this is happening at seemingly random intervals then you need to start investigating things very carefully.

These problems can usually be attributed to either:

1. If the problem is occurring only in a specific application that you are developing yourself it is probably a bug in your code.

2. If it is a problem with part of the base FreeBSD system, it may also be buggy code, but more often than not these problems are found and fixed long before us general FAQ readers get to use these bits of code (that is what -current is for).

In particular, a dead giveaway that this is not a FreeBSD bug is if you see the problem when you are compiling a program, but the activity that the compiler is carrying out changes each time.

For example, suppose you are running `make `buildworld``, and the compile fails while trying to compile `ls.c` into `ls.o`. If you then run `make `buildworld`` again, and the compile fails in the same place then this is a broken build — try updating your sources and try again. If the compile fails elsewhere then this is almost certainly hardware.

What you should do:

In the first case you can use a debugger e.g., gdb(1) to find the point in the program which is attempting to access a bogus address and then fix it.

In the second case you need to verify that it is not your hardware at fault.

Common causes of this include:

1. Your hard disks might be overheating: Check the fans in your case are still working, as your disk (and perhaps other hardware might be overheating).

2. The processor running is overheating: This might be because the processor has been overclocked, or the fan on the processor might have died. In either case you need to ensure that you have hardware running at what it is specified to run at, at least while trying to solve this problem (in other words, clock it back to the default settings.)

   If you are overclocking then note that it is far cheaper to have a slow system than a fried system that needs replacing! Also the wider community is not often sympathetic to problems on overclocked systems, whether you believe it is safe or not.

3. Dodgy memory: If you have multiple memory SIMMS/DIMMS installed then pull them all out and try running the machine with each SIMM or DIMM individually and narrow the problem down to either the problematic DIMM/SIMM or perhaps even a combination.

4. Over-optimistic Motherboard settings: In your BIOS settings, and some motherboard jumpers you have options to set various timings, mostly the defaults will be sufficient, but sometimes, setting the wait states on RAM too low, or setting the “RAM Speed: Turbo” option, or similar in the BIOS will cause strange behavior. A possible idea is to set to BIOS defaults, but it might be worth noting down your settings first!

5. Unclean or insufficient power to the motherboard. If you have any unused I/O boards, hard disks, or CD-ROMs in your system, try temporarily removing them or disconnecting the power cable from them, to see if your power supply can manage a smaller load. Or try another power supply, preferably one with a little more power (for instance, if your current power supply is rated at 250 Watts try one rated at 300 Watts).

You should also read the SIG11 FAQ (listed below) which has excellent explanations of all these problems, albeit from a Linux® viewpoint. It also discusses how memory testing software or hardware can still pass faulty memory.

Finally, if none of this has helped it is possible that you have just found a bug in FreeBSD, and you should follow the instructions to send a problem report.

There is an extensive FAQ on this at the SIG11 problem FAQ.

5.3. My system crashes with either “`Fatal trap 12: page fault in kernel mode`”, or “`panic:`”, and spits out a bunch of information. What should I do?

The FreeBSD developers are very interested in these errors, but need some more information than just the error you see. Copy your full crash message. Then consult the FAQ section on kernel panics, build a debugging kernel, and get a backtrace. This might sound difficult, but you do not need any programming skills; you just have to follow the instructions.

5.4. Why do I get the error “`maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5)`”?

The FreeBSD kernel will only allow a certain number of processes to exist at one time. The number is based on the `kern.maxusers` sysctl(8) variable. `kern.maxusers` also affects various other in-kernel limits, such as network buffers. If your machine is heavily loaded, you probably want to increase `kern.maxusers`. This will increase these other system limits in addition to the maximum number of processes.

To adjust your `kern.maxusers` value, see the File/Process Limits section of the Handbook. (While that section refers to open files, the same limits apply to processes.)

If your machine is lightly loaded, and you are simply running a very large number of processes, you can adjust this with the `kern.maxproc` tunable. If this tunable needs adjustment it needs to be defined in `/boot/loader.conf`. The tunable will not get adjusted until the system is rebooted. For more information about tuning tunables, see loader.conf(5). If these processes are being run by a single user, you will also need to adjust `kern.maxprocperuid` to be one less than your new `kern.maxproc` value. (It must be at least one less because one system program, init(8), must always be running.)

5.5. Why does sendmail give me an error reading “`mail loops back to myself`”?

You can find a detailed answer for this question in the Handbook.

5.6. Why do full screen applications on remote machines misbehave?

The remote machine may be setting your terminal type to something other than the `cons25` terminal type required by the FreeBSD console.

There are a number of possible work-arounds for this problem:

- After logging on to the remote machine, set your `TERM` shell variable to `ansi` or `sco` if the remote machine knows about these terminal types.

- Use a VT100 emulator like screen at the FreeBSD console. screen offers you the ability to run multiple concurrent sessions from one terminal, and is a neat program in its own right. Each screen window behaves like a VT100 terminal, so the `TERM` variable at the remote end should be set to `vt100`.

- Install the `cons25` terminal database entry on the remote machine. The way to do this depends on the operating system on the remote machine. The system administration manuals for the remote system should be able to help you here.

- Fire up an X server at the FreeBSD end and login to the remote machine using an X based terminal emulator such as `xterm` or `rxvt`. The `TERM` variable at the remote host should be set to `xterm` or `vt100`.

5.7. Why does it take so long to connect to my computer via `ssh` or `telnet`?

The symptom: there is a long delay between the time the TCP connection is established and the time when the client software asks for a password (or, in telnet(1)'s case, when a login prompt appears).

The problem: more likely than not, the delay is caused by the server software trying to resolve the client's IP address into a hostname. Many servers, including the Telnet and SSH servers that come with FreeBSD, do this to store the hostname in a log file for future reference by the administrator.

The remedy: if the problem occurs whenever you connect from your computer (the client) to any server, the problem is with the client; likewise, if the problem only occurs when someone connects to your computer (the server) the problem is with the server.

If the problem is with the client, the only remedy is to fix the DNS so the server can resolve it. If this is on a local network, consider it a server problem and keep reading; conversely, if this is on the global Internet, you will most likely need to contact your ISP and ask them to fix it for you.

If the problem is with the server, and this is on a local network, you need to configure the server to be able to resolve address-to-hostname queries for your local address range. See the hosts(5) and named(8) manual pages for more information. If this is on the global Internet, the problem may be that your server's resolver is not functioning correctly. To check, try to look up another host — say, `www.yahoo.com`. If it does not work, that is your problem.

Following a fresh install of FreeBSD, it is also possible that domain and name server information is missing from `/etc/resolv.conf`. This will often cause a delay in SSH, as the option `UseDNS` is set to `yes` by default in `/etc/ssh/sshd_config`. If this is causing the problem, you will either need to fill in the missing information in `/etc/resolv.conf` or set `UseDNS` to `no` in `sshd_config` as a temporary workaround.

5.8. Why does “`file: table is full`” show up repeatedly in dmesg(8)?

This error message indicates you have exhausted the number of available file descriptors on your system. Please see the kern.maxfiles section of the Tuning Kernel Limits section of the Handbook for a discussion and solution.

5.9. Why does the clock on my computer keep incorrect time?

Your computer has two or more clocks, and FreeBSD has chosen to use the wrong one.

Run dmesg(8), and check for lines that contain `Timecounter`. The one with the highest quality value that FreeBSD chose.

    # dmesg | grep Timecounter
    Timecounter "i8254" frequency 1193182 Hz quality 0
    Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
    Timecounter "TSC" frequency 2998570050 Hz quality 800
    Timecounters tick every 1.000 msec

You can confirm this by checking the `kern.timecounter.hardware` sysctl(3).

    # sysctl kern.timecounter.hardware
    kern.timecounter.hardware: ACPI-fast

It may be a broken ACPI timer. The simplest solution is to disable the ACPI timer in `/boot/loader.conf`:

    debug.acpi.disabled="timer"

Or the BIOS may modify the TSC clock—perhaps to change the speed of the processor when running from batteries, or going into a power saving mode, but FreeBSD is unaware of these adjustments, and appears to gain or lose time.

In this example, the `i8254` clock is also available, and can be selected by writing its name to the `kern.timecounter.hardware` sysctl(3).

    # sysctl kern.timecounter.hardware=i8254
    kern.timecounter.hardware: TSC -> i8254

Your computer should now start keeping more accurate time.

To have this change automatically run at boot time, add the following line to `/etc/sysctl.conf`:

    kern.timecounter.hardware=i8254

5.10. What does the error “`swap_pager: indefinite wait buffer:`” mean?

This means that a process is trying to page memory to disk, and the page attempt has hung trying to access the disk for more than 20 seconds. It might be caused by bad blocks on the disk drive, disk wiring, cables, or any other disk I/O-related hardware. If the drive itself is actually bad, you will also see disk errors in `/var/log/messages` and in the output of `dmesg`. Otherwise, check your cables and connections.

5.11. What is a “`lock order reversal`”?

The FreeBSD kernel uses a number of resource locks to arbitrate contention for certain resources. When multiple kernel threads try to obtain multiple resource locks, there's always the potential for a deadlock, where two threads have each obtained one of the locks and blocks forever waiting for the other thread to release one of the other locks. This sort of locking problem can be avoided if all threads obtain the locks in the same order.

A run-time lock diagnostic system called witness(4), enabled in FreeBSD-CURRENT and disabled by default for stable branches and releases, detects the potential for deadlocks due to locking errors, including errors caused by obtaining multiple resource locks with a different order from different parts of the kernel. The witness(4) framework tries to detect this problem as it happens, and reports it by printing a message to the system console about a “`lock order reversal`” (often referred to also as LOR).

It is possible to get false positives, as witness(4) is conservative. A true positive report does not mean that a system is dead-locked; instead it should be understood as a warning of the form “if you were unlucky, a deadlock would have happened here”.

> Note: Problematic LORs tend to get fixed quickly, so check http://lists.FreeBSD.org/mailman/listinfo/freebsd-current before posting to the mailing lists.

5.12. What does “`Called ... with the following non-sleepable locks held`” mean?

This means that a function that may sleep was called while a mutex (or other unsleepable) lock was held.

The reason this is an error is because mutexes are not intended to be held for long periods of time; they are supposed to only be held to maintain short periods of synchronization. This programming contract allows device drivers to use mutexes to synchronize with the rest of the kernel during interrupts. Interrupts (under FreeBSD) may not sleep. Hence it is imperative that no subsystem in the kernel block for an extended period while holding a mutex.

To catch such errors, assertions may be added to the kernel that interact with the witness(4) subsystem to emit a warning or fatal error (depending on the system configuration) when a potentially blocking call is made while holding a mutex.

In summary, such warnings are non-fatal, however with unfortunate timing they could cause undesirable effects ranging from a minor blip in the system's responsiveness to a complete system lockup.

For additional information about locking in FreeBSD see locking(9).

5.13. Why does `buildworld`/`installworld` die with the message “`touch: not found`”?

This error does not mean that the touch(1) utility is missing. The error is instead probably due to the dates of the files being set sometime in the future. If your CMOS-clock is set to local time you need to run the command `adjkerntz -i` to adjust the kernel clock when booting into single user mode.

# Chapter 6 User Applications

6.1. So, where are all the user applications?
6.2. How do I download the Ports tree? Should I be using SVN?
6.3. Does FreeBSD support Java™?
6.4. Why can I not build this port on my 8.`X` -, or 9.`X` -STABLE machine?
6.5. I just tried to build `INDEX` using `make `index``, and it failed. Why?
6.6. I updated the sources, now how do I update my installed ports?
6.7. Do I need to recompile every port each time I perform a major version update?
6.8. Do I need to recompile every port each time I perform a minor version update?
6.9. Why is `/bin/sh` so minimal? Why does FreeBSD not use `bash` or another shell?
6.10. How do I create audio CDs from my MIDI files?
6.11. Where can I get an Office Suite for FreeBSD?
6.12. Are there any Database systems for FreeBSD?
6.13. How can I convert from pkgng to the old package tools?

6.1. So, where are all the user applications?

Please take a look at the ports page for info on software packages ported to FreeBSD. The list currently tops 24,000 and is growing daily, so come back to check often or subscribe to the FreeBSD announcements mailing list for periodic updates on new entries.

Most ports should work on the 8.`X`, and 9.`X` branches. Each time a FreeBSD release is made, a snapshot of the ports tree at the time of release in also included in the `ports/` directory.

We also support the concept of a “package”, essentially no more than a compressed binary distribution with a little extra intelligence embedded in it for doing whatever custom installation work is required. A package can be installed and uninstalled again easily without having to know the gory details of which files it includes.

Use pkg_add(1) on the specific package files you are interested in installing. Package files can usually be identified by their `.tbz` suffix and CD-ROM distribution people will have a `packages/All` directory on their CD which contains such files. They can also be downloaded over the net for various versions of FreeBSD at the following locations:

for 8.`X` -RELEASE/8-STABLE

  ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-8-stable

for 9.`X` -RELEASE/9-STABLE

  ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-9-stable

or your nearest local mirror site.

Note that all ports may not be available as packages since new ones are constantly being added. It is always a good idea to check back periodically to see which packages are available at the ftp.FreeBSD.org master site.

6.2. How do I download the Ports tree? Should I be using SVN?

Any of the methods listed here work:

- Use portsnap for most use cases.

- Use SVN directly if you need custom patches to the ports tree.

- Use CTM if you prefer getting patches by email (this is a rarer use case).

Any other method should be considered a legacy method. If you do not already use them, do not start.

6.3. Does FreeBSD support Java™?

Yes. Please see http://www.FreeBSD.org/java/.

6.4. Why can I not build this port on my 8.`X` -, or 9.`X` -STABLE machine?

If you are running a FreeBSD version that lags significantly behind -CURRENT or -STABLE, you may need to update your Ports Collection; see the Keeping Up section of the Porter's Handbook for further information on how to do this. If you are up to date, then someone might have committed a change to the port which works for -CURRENT but which broke the port for -STABLE. Please submit a bug report on this with the send-pr(1) command, since the Ports Collection is supposed to work for both the -CURRENT and -STABLE branches.

6.5. I just tried to build `INDEX` using `make `index``, and it failed. Why?

First, always make sure that you have a complete up-to-date Ports Collection. Errors that affect building `INDEX` from an up-to-date copy of the Ports Collection are high-visibility and are thus almost always fixed immediately.

There are rare cases where `INDEX` will not build due to odd cases involving `WITH_`*`` or `WITHOUT_`*`` variables being set in `make.conf`. If you suspect that this is the case, please try to make `INDEX` with those make variables turned off before reporting it to FreeBSD ports mailing list.

6.6. I updated the sources, now how do I update my installed ports?

FreeBSD does not include a port upgrading tool, but it does have some tools to make the upgrade process somewhat easier. You can also install additional tools to simplify port handling, see the Upgrading Ports section in the FreeBSD Handbook.

6.7. Do I need to recompile every port each time I perform a major version update?

By all means! While a recent system will run with software compiled under an older release, you will end up with things randomly crashing and failing to work once you start installing other ports or updating a portion of what you already have.

When the system is upgraded, various shared libraries, loadable modules, and other parts of the system will be replaced with newer versions. Applications linked against the older versions may fail to start or, in other cases, fail to function properly.

For more information, see the section on upgrades in the FreeBSD Handbook.

6.8. Do I need to recompile every port each time I perform a minor version update?

In general, no. FreeBSD developers do their utmost to guarantee binary compatibility across all releases with the same major version number. Any exceptions will be documented in the Release Notes, and advice given there should be followed.

6.9. Why is `/bin/sh` so minimal? Why does FreeBSD not use `bash` or another shell?

Many people need to write shell scripts which will be portable across many systems. That is why POSIX® specifies the shell and utility commands in great detail. Most scripts are written in Bourne shell (sh(1)), and because several important programming interfaces (make(1), system(3), popen(3), and analogues in higher-level scripting languages like Perl and Tcl) are specified to use the Bourne shell to interpret commands. Because the Bourne shell is so often and widely used, it is important for it to be quick to start, be deterministic in its behavior, and have a small memory footprint.

The existing implementation is our best effort at meeting as many of these requirements simultaneously as we can. To keep `/bin/sh` small, we have not provided many of the convenience features that other shells have. That is why other more featureful shells like `bash`, `scsh`, tcsh(1), and `zsh` are available. (You can compare for yourself the memory utilization of all these shells by looking at the “VSZ” and “RSS” columns in a `ps `-u`` listing.)

6.10. How do I create audio CDs from my MIDI files?

To create audio CDs from MIDI files, first install `audio/timidity++` from ports then install manually the GUS patches set by Eric A. Welsh, available at http://alleg.sourceforge.net/digmid.html. After TiMidity++ has been installed properly, MIDI files may be converted to WAV files with the following command line:

    % timidity -Ow -s 44100 -o /tmp/juke/01.wav 01.mid

The WAV files can then be converted to other formats or burned onto audio CDs, as described in the FreeBSD Handbook.

6.11. Where can I get an Office Suite for FreeBSD?

The open-source Apache OpenOffice and LibreOffice office suites work natively on FreeBSD.

FreeBSD also includes a variety of text editors, spreadsheets, and drawing programs in the Ports Collection.

6.12. Are there any Database systems for FreeBSD?

Yes! See the Commercial Vendors section of FreeBSD's Web site.

Also see the Databases section of the Ports Collection.

6.13. How can I convert from pkgng to the old package tools?

Short answer: it is not possible.

Longer answer: if you have made any changes using `pkg` converting back is non-trivial and requires lots of manual editing of internal package database files. However, if you have just run `pkg2ng` then you may remove `/var/db/pkg/local.sqlite` and extract `/var/backups/pkgdb.bak.tbz`.

# Chapter 7 Kernel Configuration

7.1. I would like to customize my kernel. Is it difficult?
7.2. Why is my kernel so big?
7.3. Why does every kernel I try to build fail to compile, even `GENERIC`?
7.4. How can I verify which scheduler is in use on a running system?
7.5. What is `kern.sched.quantum`?

7.1. I would like to customize my kernel. Is it difficult?

Not at all! Check out the kernel config section of the Handbook.

> Note: The new `kernel` will be installed to the `/boot/kernel` directory along with its modules, while the old kernel and its modules will be moved to the `/boot/kernel.old` directory, so if you make a mistake the next time you play with your configuration you can boot the previous version of your kernel.

7.2. Why is my kernel so big?

`GENERIC` kernels shipped with FreeBSD and later are compiled in debug mode. Kernels built in debug mode contain many symbols in separate files that are used for debugging, thus greatly increasing the size of `/boot/kernel/`. Note that there will be little or no performance loss from running a debug kernel, and it is useful to keep one around in case of a system panic.

However, if you are running low on disk space, there are different options to reduce the size of `/boot/kernel/`.

If you do not want the symbol files to be installed, make sure you have the following line present in `/etc/src.conf`:

    WITHOUT_KERNEL_SYMBOLS=yes

For more information see src.conf(5).

If you do not want to build a debug kernel, make sure that both of the following are true:

- You do not have a line in your kernel configuration file that reads:

      makeoptions DEBUG=-g

- You are not running config(8) with `-g`.

Either of the above settings will cause your kernel to be built in debug mode. As long as you make sure you follow the steps above, you can build your kernel normally.

If you want only the modules you use to be built and installed, make sure you have a line like below in `/etc/make.conf`:

    MODULES_OVERRIDE= accf_http ipfw

Replace accf_httpd ipfw with a list of modules you need. Only these modules will be built. This does not only reduce the size of the kernel directory but also decreases the amount of time needed to build your kernel. For more information see `/usr/share/examples/etc/make.conf`.

You can also remove unneeded devices from your kernel to further reduce the size. See Q: 7.1. for more information.

To put any of these options into effect you will have to build and install your new kernel.

Most kernels (`/boot/kernel/kernel`) tend to be around 12 MB to 16 MB.

7.3. Why does every kernel I try to build fail to compile, even `GENERIC`?

There are a number of possible causes for this problem. They are, in no particular order:

- You are not using the `make `buildkernel`` and `make `installkernel`` targets, and your source tree is different from the one used to build the currently running system (e.g., you are compiling 9.1-RELEASE on a 8.4-RELEASE system). If you are attempting an upgrade, please read `/usr/src/UPDATING`, paying particular attention to the “COMMON ITEMS” section at the end.

- You are using the `make `buildkernel`` and `make `installkernel`` targets, but you failed to assert the completion of the `make `buildworld`` target. The `make `buildkernel`` target relies on files generated by the `make `buildworld`` target to complete its job correctly.

- Even if you are trying to build FreeBSD-STABLE, it is possible that you fetched the source tree at a time when it was either being modified, or broken for other reasons; only releases are absolutely guaranteed to be buildable, although FreeBSD-STABLE builds fine the majority of the time. If you have not already done so, try re-fetching the source tree and see if the problem goes away. Try using a different server in case the one you are using is having problems.

7.4. How can I verify which scheduler is in use on a running system?

The name of the scheduler currently being used is directly available as the value of the `kern.sched.name` sysctl:

    % sysctl kern.sched.name
    kern.sched.name: ULE

7.5. What is `kern.sched.quantum`?

`kern.sched.quantum` is the maximum number of ticks a process can run without being preempted in the 4BSD scheduler.

# Chapter 8 Disks, File Systems, and Boot Loaders

8.1. How can I add my new hard disk to my FreeBSD system?
8.2. How do I move my system over to my huge new disk?
8.3. Which partitions can safely use Soft Updates? I have heard that Soft Updates on `/` can cause problems. What about Journaled Soft Updates?
8.4. Can I mount other foreign file systems under FreeBSD?
8.5. How do I mount a secondary DOS partition?
8.6. Is there a cryptographic file system for FreeBSD?
8.7. How can I use the Windows NT® loader to boot FreeBSD?
8.8. How do I boot FreeBSD and Linux from LILO?
8.9. How do I boot FreeBSD and Linux using GRUB?
8.10. How do I boot FreeBSD and Linux using BootEasy?
8.11. How do I change the boot prompt from `???` to something more meaningful?
8.12. I have a new removable drive, how do I use it?
8.13. Why do I get “`Incorrect super block`” when mounting a CD-ROM?
8.14. Why do I get “`Device not configured`” when mounting a CD-ROM?
8.15. Why do all non-English characters in filenames show up as “?” on my CDs when mounted in FreeBSD?
8.16. I burned a CD under FreeBSD and now I can not read it under any other operating system. Why?
8.17. How can I create an image of a data CD?
8.18. Why can I not `mount` an audio CD?
8.19. How do I `mount` a multi-session CD?
8.20. How do I let ordinary users mount CD-ROMs, DVDs, USB drives, and other removable media?
8.21. The `du` and `df` commands show different amounts of disk space available. What is going on?
8.22. How can I add more swap space?
8.23. Why does FreeBSD see my disk as smaller than the manufacturer says it is?
8.24. How is it possible for a partition to be more than 100% full?

8.1. How can I add my new hard disk to my FreeBSD system?

See the Adding Disks section in the FreeBSD Handbook.

8.2. How do I move my system over to my huge new disk?

The best way is to reinstall the OS on the new disk, then move the user data over. This is highly recommended if you have been tracking -STABLE for more than one release, or have updated a release instead of installing a new one. You can install booteasy on both disks with boot0cfg(8), and dual boot them until you are happy with the new configuration. Skip the next paragraph to find out how to move the data after doing this.

Alternatively, partition and label the new disk with either sade(8) or gpart(8). If the disks are MBR-formatted, you can also install booteasy on both disks with boot0cfg(8), so that you can dual boot to the old or new system after the copying is done.

Now you have the new disk set up, and are ready to move the data. Unfortunately, you cannot just blindly copy the data. Things like device files (in `/dev`), flags, and links tend to screw that up. You need to use tools that understand these things, which means dump(8). Although it is suggested that you move the data in single user mode, it is not required.

You should never use anything but dump(8) and restore(8) to move the root file system. The tar(1) command may work — then again, it may not. You should also use dump(8) and restore(8) if you are moving a single partition to another empty partition. The sequence of steps to use `dump` to move a partitions data to a new partition is:

1. `newfs` the new partition.

2. `mount` it on a temporary mount point.

3. `cd` to that directory.

4. `dump` the old partition, piping output to the new one.

For example, if you are going to move root to `/dev/`ada1s1a``, with ``/mnt`` as the temporary mount point, it is:

    # newfs /dev/ada1s1a
    # mount /dev/ada1s1a /mnt
    # cd /mnt
    # dump 0af - / | restore rf -

Rearranging your partitions with `dump` takes a bit more work. To merge a partition like `/var` into its parent, create the new partition large enough for both, move the parent partition as described above, then move the child partition into the empty directory that the first move created:

    # newfs /dev/ada1s1a
    # mount /dev/ada1s1a /mnt
    # cd /mnt
    # dump 0af - / | restore rf -
    # cd var
    # dump 0af - /var | restore rf -

To split a directory from its parent, say putting `/var` on its own partition when it was not before, create both partitions, then mount the child partition on the appropriate directory in the temporary mount point, then move the old single partition:

    # newfs /dev/ada1s1a
    # newfs /dev/ada1s1d
    # mount /dev/ada1s1a /mnt
    # mkdir /mnt/var
    # mount /dev/ada1s1d /mnt/var
    # cd /mnt
    # dump 0af - / | restore rf -

You might prefer cpio(1), pax(1), tar(1) to dump(8) for user data. At the time of this writing, these are known to lose file flag information, so use them with caution.

8.3. Which partitions can safely use Soft Updates? I have heard that Soft Updates on `/` can cause problems. What about Journaled Soft Updates?

Short answer: you can usually use Soft Updates safely on all partitions.

Long answer: Soft Updates has two characteristics that may be undesirable on certain paritions. First, a Soft Updates partition has a small chance of losing data during a system crash. (The partition will not be corrupted; the data will simply be lost.) Second, Soft Updates can cause temporary space shortages.

When using Soft Updates, the kernel can take up to thirty seconds to write changes to the physical disk. When a large file is deleted the file still resides on disk until the kernel actually performs the deletion. This can cause a very simple race condition. Suppose you delete one large file and immediately create another large file. The first large file is not yet actually removed from the physical disk, so the disk might not have enough room for the second large file. You get an error that the partition does not have enough space, although you know perfectly well that you just released a large chunk of space! When you try again mere seconds later, the file creation works as you expect. This has left more than one user scratching his head and doubting his sanity, the FreeBSD file system, or both.

If a system should crash after the kernel accepts a chunk of data for writing to disk, but before that data is actually written out, data could be lost. This risk is extremely small, but generally manageable.

These issues affect all partitions using Soft Updates. So, what does this mean for the root partition?

Vital information on the root partition changes very rarely. If the system crashed during the thirty-second window after such a change is made, it is possible that data could be lost. This risk is negligible for most applications, but you should be aware that it exists. If your system cannot tolerate this much risk, do not use Soft Updates on the root file system!

`/` is traditionally one of the smallest partitions. If you put the `/tmp` directory on `/` and you have a busy `/tmp`, you might see intermittent space problems. Symlinking `/tmp` to `/var/tmp` will solve this problem.

Finally, dump(8) does not work in live mode (-L) on a filesystem, with Journaled Soft Updates (SU+J).

8.4. Can I mount other foreign file systems under FreeBSD?

FreeBSD supports a variety of other file systems.

UFS

  UFS CD-ROMs can be mounted directly on FreeBSD. Mounting disk partitions from Digital UNIX and other systems that support UFS may be more complex, depending on the details of the disk partitioning for the operating system in question.

ext2/ext3

  FreeBSD supports `ext2fs` and `ext3fs` partitions. See mount_ext2fs(8) for more information.

NTFS

  FUSE based NTFS support is available as a port (`sysutils/fusefs-ntfs`). For more information see ntfs-3g.

FAT

  FreeBSD includes a read-write FAT driver. For more information, see mount_msdosfs(8).

ZFS

  FreeBSD includes a port of Sun™'s ZFS driver. The current recommendation is to use it only on amd64 platforms with sufficient memory. For more information, see zfs(8).

FreeBSD also supports network file systems such as NFS (see mount_nfs(8)), NetWare (see mount_nwfs(8)), and Microsoft-style SMB file systems (see mount_smbfs(8)). You can find ports based on FUSE (`sysutils/fusefs-kmod`) for many other file systems.

8.5. How do I mount a secondary DOS partition?

The secondary DOS partitions are found after all the primary partitions. For example, if you have an “E” partition as the second DOS partition on the second SCSI drive, there will be a device file for “slice 5” in `/dev`, so simply mount it:

    # mount -t msdosfs /dev/da1s5 /dos/e

8.6. Is there a cryptographic file system for FreeBSD?

Yes. You can use either gbde(8) or geli(8), see the Encrypting Disk Partitions section of the FreeBSD Handbook.

8.7. How can I use the Windows NT® loader to boot FreeBSD?

The general idea is that you copy the first sector of your native root FreeBSD partition into a file in the DOS/Windows NT partition. Assuming you name that file something like `c:\bootsect.bsd` (inspired by `c:\bootsect.dos`), you can then edit `c:\boot.ini` to come up with something like this:

    [boot loader]
    timeout=30
    default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
    [operating systems]
    multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows NT"
    C:\BOOTSECT.BSD="FreeBSD"
    C:\="DOS"

If FreeBSD is installed on the same disk as the Windows NT boot partition simply copy `/boot/boot1` to `C:\BOOTSECT.BSD`. However, if FreeBSD is installed on a different disk `/boot/boot1` will not work, `/boot/boot0` is needed.

`/boot/boot0` needs to be installed using sysinstall(8) by selecting the FreeBSD boot manager on the screen which asks if you wish to use a boot manager. This is because `/boot/boot0` has the partition table area filled with NULL characters but sysinstall(8) copies the partition table before copying `/boot/boot0` to the MBR.

> Warning: Do not simply copy `/boot/boot0` instead of `/boot/boot1`; you will overwrite your partition table and render your computer un-bootable!

When the FreeBSD boot manager runs it records the last OS booted by setting the active flag on the partition table entry for that OS and then writes the whole 512-bytes of itself back to the MBR so if you just copy `/boot/boot0` to `C:\BOOTSECT.BSD` then it writes an empty partition table, with the active flag set on one entry, to the MBR.

8.8. How do I boot FreeBSD and Linux from LILO?

If you have FreeBSD and Linux on the same disk, just follow LILO's installation instructions for booting a non-Linux operating system. Very briefly, these are:

Boot Linux, and add the following lines to `/etc/lilo.conf`:

    other=/dev/hda2
            table=/dev/hda
            label=FreeBSD

(the above assumes that your FreeBSD slice is known to Linux as `/dev/hda2`; tailor to suit your setup). Then, run `lilo` as `root` and you should be done.

If FreeBSD resides on another disk, you need to add `loader=/boot/chain.b` to the LILO entry. For example:

    other=/dev/dab4
            table=/dev/dab
            loader=/boot/chain.b
            label=FreeBSD

In some cases you may need to specify the BIOS drive number to the FreeBSD boot loader to successfully boot off the second disk. For example, if your FreeBSD SCSI disk is probed by BIOS as BIOS disk 1, at the FreeBSD boot loader prompt you need to specify:

    Boot: 1:da(0,a)/boot/kernel/kernel

You can configure boot(8) to automatically do this for you at boot time.

The Linux+FreeBSD mini-HOWTO is a good reference for FreeBSD and Linux interoperability issues.

8.9. How do I boot FreeBSD and Linux using GRUB?

Booting FreeBSD using GRUB is very simple. Just add the following to your configuration file `/boot/grub/menu.lst` (or `/boot/grub/grub.conf` in some systems, e.g., Red Hat Linux and its derivatives).

    title FreeBSD 6.1
    	root (hd0,a)
    	kernel /boot/loader

Where `hd0,a` points to your root partition on the first disk. If you need to specify which slice number should be used, use something like this `(hd0,2,a)`. By default, if the slice number is omitted, GRUB searches the first slice which has `a` partition.

8.10. How do I boot FreeBSD and Linux using BootEasy?

Install LILO at the start of your Linux boot partition instead of in the Master Boot Record. You can then boot LILO from BootEasy.

If you are running Windows and Linux this is recommended anyway, to make it simpler to get Linux booting again if you should need to reinstall Windows (which is a Jealous Operating System, and will bear no other Operating Systems in the Master Boot Record).

8.11. How do I change the boot prompt from `???` to something more meaningful?

You can not do that with the standard boot manager without rewriting it. There are a number of other boot managers in the `sysutils` ports category that provide this functionality.

8.12. I have a new removable drive, how do I use it?

If the drive already has a file system on it, you can use a command like this:

    # mount -t msdosfs /dev/da0s1 /mnt

If the drive will only be used with FreeBSD systems it is better idea to stick a BSD file system on it, like UFS or ZFS. You will get long filename support, at least a 2X improvement in performance, and a lot more stability. If the drive will be used by other operating systems a more portable choice, such as msdosfs, is better.

    # dd if=/dev/zero of=/dev/da0 count=2
    # gpart create -s GPT /dev/da0
    # gpart add -t freebsd-ufs /dev/da0

Finally, create a new file system:

    # newfs /dev/da0p1

and mount it:

    # mount /dev/da0s1 /mnt

It is a good idea to add a line to `/etc/fstab` (see fstab(5)) so you can just type `mount /mnt` in the future:

    /dev/da0p1 /mnt ufs rw,noauto 0 0

8.13. Why do I get “`Incorrect super block`” when mounting a CD-ROM?

You have to tell mount(8) the type of the device that you want to mount. This is described in the Handbook section on optical media, specifically the section Using Data CDs.

8.14. Why do I get “`Device not configured`” when mounting a CD-ROM?

This generally means that there is no CD-ROM in the CD-ROM drive, or the drive is not visible on the bus. Please see the Using Data CDs section of the Handbook for a detailed discussion of this issue.

8.15. Why do all non-English characters in filenames show up as “?” on my CDs when mounted in FreeBSD?

Your CD-ROM probably uses the “Joliet” extension for storing information about files and directories. This is discussed in the Handbook chapter on creating and using CD-ROMs, specifically the section on Using Data CD-ROMs.

8.16. I burned a CD under FreeBSD and now I can not read it under any other operating system. Why?

You most likely burned a raw file to your CD, rather than creating an ISO 9660 file system. Take a look at the Handbook chapter on creating CD-ROMs, particularly the section on burning raw data CDs.

8.17. How can I create an image of a data CD?

This is discussed in the Handbook section on duplicating data CDs. For more on working with CD-ROMs, see the Creating CDs Section in the Storage chapter in the Handbook.

8.18. Why can I not `mount` an audio CD?

If you try to mount an audio CD, you will get an error like “`cd9660: /dev/acd0c: Invalid argument`”. This is because `mount` only works on file systems. Audio CDs do not have file systems; they just have data. You need a program that reads audio CDs, such as the `audio/xmcd` port.

8.19. How do I `mount` a multi-session CD?

By default, mount(8) will attempt to mount the last data track (session) of a CD. If you would like to load an earlier session, you must use the `-s` command line argument. Please see mount_cd9660(8) for specific examples.

8.20. How do I let ordinary users mount CD-ROMs, DVDs, USB drives, and other removable media?

As `root` set the sysctl variable `vfs.usermount` to `1`.

    # sysctl vfs.usermount=1

To make this persist across reboots, add the line ``vfs.usermount`=1` to `/etc/sysctl.conf` so that it is reset at system boot time.

Users can only mount devices they have read permissions to. To allow users to mount a device permissions must be set in `/etc/devfs.conf`.

For example, to allow users to mount the first USB drive add:

    # Allow all users to mount a USB drive.
    	    own       /dev/da0       root:operator
    	    perm      /dev/da00       0666

All users can now mount devices they could read onto a directory that they own:

    % mkdir ~/my-mount-point
    % mount -t msdosfs /dev/da0~/my-mount-point

Unmounting the device is simple:

    % umount ~/my-mount-point

Enabling `vfs.usermount`, however, has negative security implications. A better way to access MS-DOS® formatted media is to use the `emulators/mtools` package in the Ports Collection.

> Note: The device name used in the previous examples must be changed according to your configuration.

8.21. The `du` and `df` commands show different amounts of disk space available. What is going on?

You need to understand what `du` and `df` really do. `du` goes through the directory tree, measures how large each file is, and presents the totals. `df` just asks the file system how much space it has left. They seem to be the same thing, but a file without a directory entry will affect `df` but not `du`.

When a program is using a file, and you delete the file, the file is not really removed from the file system until the program stops using it. The file is immediately deleted from the directory listing, however. You can see this easily enough with a program such as `more`. Assume you have a file large enough that its presence affects the output of `du` and `df`. (Since disks can be so large today, this might be a very large file!) If you delete this file while using `more` on it, `more` does not immediately choke and complain that it cannot view the file. The entry is simply removed from the directory so no other program or user can access it. `du` shows that it is gone — it has walked the directory tree and the file is not listed. `df` shows that it is still there, as the file system knows that `more` is still using that space. Once you end the `more` session, `du` and `df` will agree.

This situation is common on web servers. Many people set up a FreeBSD web server and forget to rotate the log files. The access log fills up `/var`. The new administrator deletes the file, but the system still complains that the partition is full. Stopping and restarting the web server program would free the file, allowing the system to release the disk space. To prevent this from happening, set up newsyslog(8).

Note that Soft Updates can delay the freeing of disk space; you might need to wait up to 30 seconds for the change to be visible!

8.22. How can I add more swap space?

In the Configuration and Tuning section of the Handbook, you will find a section describing how to do this.

8.23. Why does FreeBSD see my disk as smaller than the manufacturer says it is?

Disk manufacturers calculate gigabytes as a billion bytes each, whereas FreeBSD calculates them as 1,073,741,824 bytes each. This explains why, for example, FreeBSD's boot messages will report a disk that supposedly has 80 GB as holding 76,319 MB.

Also note that FreeBSD will (by default) reserve 8% of the disk space.

8.24. How is it possible for a partition to be more than 100% full?

A portion of each UFS partition (8%, by default) is reserved for use by the operating system and the `root` user. df(1) does not count that space when calculating the `Capacity` column, so it can exceed 100%. Also, you will notice that the `Blocks` column is always greater than the sum of the `Used` and `Avail` columns, usually by a factor of 8%.

For more details, look up `-m` in tunefs(8).

## 8.1 ZFS

8.1.1. What is the minimum amount of RAM one should have to run ZFS?
8.1.2. What is the ZIL and when does it get used?
8.1.3. Do I need a SSD for ZIL?
8.1.4. What is the L2ARC?
8.1.5. Is enabling deduplication advisable?
8.1.6. I can not delete or create files on my ZFS pool. How can I fix this?
8.1.7. Does ZFS support TRIM for Solid State Drives?

8.1.1. What is the minimum amount of RAM one should have to run ZFS?

A minimum of 4GB of RAM is required for comfortable usage, but individual workloads can vary widely.

8.1.2. What is the ZIL and when does it get used?

The ZIL ((ZFS intent log) is a write log used to implement posix write commitment semantics across crashes. Normally writes are bundled up into transaction groups and written to disk when filled (“Transaction Group Commit”). However syscalls like fsync(2) require a commitment that the data is written to stable storage before returning. The ZIL is needed for writes that have been acknowledged as written but which are not yet on disk as part of a transaction. The transaction groups are timestamped. In the event of a crash the last valid timestamp is found and missing data is merged in from the ZIL.

8.1.3. Do I need a SSD for ZIL?

By default, ZFS stores the ZIL in the pool with all the data. If your application has a heavy write load, storing the ZIL in a separate device that has very fast synchronous, sequential write performance can improve overall system. For other workloads, a SSD is unlikely to make much of an improvement.

8.1.4. What is the L2ARC?

The L2ARC is a read cache stored on a fast device such as an SSD. This cache is not persisent across reboots. Note that RAM is used as the first layer of cache and the L2ARC is only needed if there is insufficient RAM.

L2ARC needs space in the ARC to index it. So, perversely, a working set that fits perfectly in the ARC will not fit perfectly any more if a L2ARC is used because part of the ARC is holding the L2ARC index, pushing part of the working set into the L2ARC which is slower than RAM.

8.1.5. Is enabling deduplication advisable?

Generally speaking, no.

Deduplication takes up a significant amount of RAM and may slow down read and write disk access times. Unless one is storing data that is very heavily duplicated (such as virtual machine images, or user backups) it is possible that deduplication will do more harm than good. Another consideration is the inability to revert deduplication status. If data is written when deduplication is enabled, disabling dedup will not cause those blocks which were deduplicated to be replicated until they are next modified.

Deduplication can also lead to some unexpected situations. In particular deleting files may become much slower.

8.1.6. I can not delete or create files on my ZFS pool. How can I fix this?

This could happen because the pool is 100% full. ZFS requires space on the disk to write transaction metadata. To restore the pool to a usable state, truncate a file you want to delete.

    % truncate -s 0 unimportant-file

File truncation works because a new transaction is not started, new spare blocks are created instead.

> Note: On systems with additional ZFS dataset tuning, such as deduplication, the space may not be immediately available

8.1.7. Does ZFS support TRIM for Solid State Drives?

ZFS TRIM support was added to FreeBSD 10-CURRENT with revision r`240868`. ZFS TRIM support is not yet available on the -STABLE branches.

ZFS TRIM is enabled by default, and can be turned off by adding this line to `/etc/sysctl.conf`:

    vfs.zfs.trim_disable=1

> Note: ZFS TRIM may not work with all configurations, such as a ZFS filesystem on a GELI-backed device.

# Chapter 9 System Administration

9.1. Where are the system start-up configuration files?
9.2. How do I add a user easily?
9.3. Why do I keep getting messages like “`root: not found`” after editing `/etc/crontab`
9.4. Why do I get the error, “`you are not in the correct group to su root`” when I try to `su` to `root`?
9.5. I made a mistake in `rc.conf`, or another startup file, and now I cannot edit it because the file system is read-only. What should I do?
9.6. Why am I having trouble setting up my printer?
9.7. How can I correct the keyboard mappings for my system?
9.8. Why can I not get user quotas to work properly?
9.9. Does FreeBSD support System V IPC primitives?
9.10. What other mail-server software can I use instead of sendmail?
9.11. I have forgotten the `root` password! What do I do?
9.12. How do I keep Control+Alt+Delete from rebooting the system?
9.13. How do I reformat DOS text files to UNIX ones?
9.14. How do I kill processes by name?
9.15. How do I re-read `/etc/rc.conf` and re-start `/etc/rc` without a reboot?
9.16. I tried to update my system to the latest -STABLE, but got -BETA`x`, -RC or -PRERELEASE! What is going on?
9.17. I tried to install a new kernel, and the chflags(1) failed. How do I get around this?
9.18. I cannot change the time on my system by more than one second! How do I get around this?
9.19. Why is `rpc.statd` using 256 MB of memory?
9.20. Why can I not unset the `schg` file flag?
9.21. Why does SSH authentication through `.shosts` not work by default in recent versions of FreeBSD?
9.22. What is `vnlru`?
9.23. What do the various memory states displayed by `top` mean?
9.24. How much free memory is available?
9.25. What is `/var/empty`? I can not delete it!
9.26. I just changed `/etc/newsyslog.conf`. How can I check if it does what I expect?
9.27. My time is wrong, how can I change the timezone?

9.1. Where are the system start-up configuration files?

The primary configuration file is `/etc/defaults/rc.conf` (see rc.conf(5)). System startup scripts such as `/etc/rc` and `/etc/rc.d` (see rc(8)) just include this file. Do not edit this file! Instead, if there is any entry in `/etc/defaults/rc.conf` that you want to change, you should copy the line into `/etc/rc.conf` and change it there.

For example, if you wish to start named(8), the included DNS server, all you need to do is:

    # echo 'named_enable="YES"' >> /etc/rc.conf

To start up local services, place shell scripts in the `/usr/local/etc/rc.d` directory. These shell scripts should be set executable, the default file mode is `555`.

9.2. How do I add a user easily?

Use the adduser(8) command, or the pw(8) command for more complicated situations.

To remove the user, use the rmuser(8) command or, if necessary, pw(8).

9.3. Why do I keep getting messages like “`root: not found`” after editing `/etc/crontab`

This is normally caused by editing the system crontab (`/etc/crontab`) and then using crontab(1) to install it:

    # crontab /etc/crontab

This is not the correct way to do things. The system crontab has a different format to the per-user crontabs which crontab(1) updates (the crontab(5) manual page explains the differences in more detail).

If this is what you did, the extra crontab is simply a copy of `/etc/crontab` in the wrong format it. Delete it with the command:

    # crontab -r

Next time, when you edit `/etc/crontab`, you should not do anything to inform cron(8) of the changes, since it will notice them automatically.

If you want something to be run once per day, week, or month, it is probably better to add shell scripts `/usr/local/etc/periodic`, and let the periodic(8) command run from the system `cron` schedule it with the other periodic system tasks.

The actual reason for the error is that the system crontab has an extra field, specifying which user to run the command as. In the default system crontab provided with FreeBSD, this is `root` for all entries. When this crontab is used as the `root` user's crontab (which is not the same as the system crontab), cron(8) assumes the string `root` is the first word of the command to execute, but no such command exists.

9.4. Why do I get the error, “`you are not in the correct group to su root`” when I try to `su` to `root`?

This is a security feature. To `su` to `root` (or any other account with superuser privileges), you must be in the `wheel` group. If this feature were not there, anybody with an account on a system who also found out `root`'s password would be able to gain superuser level access to the system. With this feature, this is not strictly true; su(1) will prevent them from even trying to enter the password if they are not in `wheel`.

To allow someone to `su` to `root`, simply put them in the `wheel` group. Use pw(8) for this purpose.

    # pw groupmod wheel -m lisa

The above example will add user `lisa` to the group `wheel`.

9.5. I made a mistake in `rc.conf`, or another startup file, and now I cannot edit it because the file system is read-only. What should I do?

Restart the system using `boot -s` at the loader prompt to enter Single User mode. When prompted for a shell pathname, simply press Enter, and run `mount -urw /` to re-mount the root file system in read/write mode. You may also need to run `mount -a -t ufs` to mount the file system where your favorite editor is defined. If your favorite editor is on a network file system, you will need to either configure the network manually before you can mount network file systems, or use an editor which resides on a local file system, such as ed(1).

If you intend to use a full screen editor such as vi(1) or emacs(1), you may also need to run `export TERM=xterm` on FreeBSD 9.0+, or `export TERM=cons25` on FreeBSD 8.X so that these editors can load the correct data from the termcap(5) database.

Once you have performed these steps, you can edit `/etc/rc.conf` as you usually would to fix the syntax error. The error message displayed immediately after the kernel boot messages should tell you the number of the line in the file which is at fault.

9.6. Why am I having trouble setting up my printer?

See the Handbook entry on printing. It should cover most of your problem.

Some printers require a host-based driver to do any kind of printing. These so-called “WinPrinters” are not natively supported by FreeBSD. If your printer does not work in DOS or Windows, it is probably a WinPrinter. Your only hope of getting one of these to work is to check if the `print/pnm2ppa` port supports it.

9.7. How can I correct the keyboard mappings for my system?

Please see the Handbook section on using localization, specifically the section on console setup.

9.8. Why can I not get user quotas to work properly?

- It is possible that your kernel is not configured to use quotas. If this is the case, you will need to add the following line to your kernel configuration file and recompile:

      options QUOTA

  Please read the Handbook entry on quotas for full details.

- Do not turn on quotas on `/`.

- Put the quota file on the file system that the quotas are to be enforced on, i.e.:

  File System | Quota file
  --- | ---
  `/usr` | `/usr/admin/quotas`
  `/home` | `/home/admin/quotas`
  … | …

9.9. Does FreeBSD support System V IPC primitives?

Yes, FreeBSD supports System V-style IPC, including shared memory, messages and semaphores, in the `GENERIC` kernel. With a custom kernel, support may be loaded with the `sysvshm.ko`, `sysvsem.ko` and `sysvmsg.ko` kernel modules, or enabled in the custom kernel by adding the following lines to your kernel config:

    options    SYSVSHM          # enable shared memory
    options    SYSVSEM          # enable for semaphores
    options    SYSVMSG          # enable for messaging

Recompile and install your kernel.

9.10. What other mail-server software can I use instead of sendmail?

The sendmail server is the default mail-server software for FreeBSD, but you can easily replace it with one of the other MTA (for instance, an MTA installed from the ports).

There are various alternative MTAs in the ports tree already, with `mail/exim`, `mail/postfix`, `mail/qmail`, and `mail/zmailer` being some of the most popular choices.

Diversity is nice, and the fact that you have many different mail-servers to chose from is considered a good thing; therefore try to avoid asking questions like “Is sendmail better than qmail?” in the mailing lists. If you do feel like asking, first check the mailing list archives. The advantages and disadvantages of each and every one of the available MTAs have already been discussed a few times.

9.11. I have forgotten the `root` password! What do I do?

Do not panic! Restart the system, type `boot -s` at the `Boot:` prompt to enter Single User mode. At the question about the shell to use, hit Enter. You will be dropped to a `#` prompt. Enter `mount -urw /` to remount your root file system read/write, then run `mount -a` to remount all the file systems. Run `passwd root` to change the `root` password then run exit(1) to continue booting.

> Note: If you are still prompted to give the `root` password when entering the Single User mode, it means that the console has been marked as `insecure` in `/etc/ttys`. In this case it will be required to boot from a FreeBSD installation disk, choose the Live CD or Shell at the beginning of the install process and issue the commands mentioned above. You will need to mount the specific partition in this case and then chroot to it, i.e., replace `mount -urw /` by `mount /dev/ada0p1 /mnt; chroot /mnt` for a system on `ada0p1`.

> Note: If you cannot mount your root partition from Single User mode, it is possible that the partitions are encrypted and it is impossible to mount them without the access keys. Your chances depend on the chosen implementation. For more information see the section about encrypted disks in the FreeBSD Handbook.

9.12. How do I keep Control+Alt+Delete from rebooting the system?

If you are using syscons(4) (the default console driver) build and install a new kernel with the line in the configuration file:

    options SC_DISABLE_REBOOT

This can also be done by setting the following sysctl(8) which does not require a reboot or kernel recompile:

    # sysctl hw.syscons.kbd_reboot=0

> Note: The above two methods are exclusive: The sysctl(8) does not exist if you compile your kernel with the `SC_DISABLE_REBOOT` option.

9.13. How do I reformat DOS text files to UNIX ones?

Use this perl(1) command:

    % perl -i.bak -npe 's/\r\n/\n/g' file(s)

where `file(s)` is one or more files to process. The modification is done in-place, with the original file stored with a `.bak` extension.

Alternatively you can use the tr(1) command:

    % tr -d '\r' < dos-text-file > unix-file

`dos-text-file` is the file containing DOS text while `unix-file` will contain the converted output. This can be quite a bit faster than using `perl`.

Yet another way to reformat DOS text files is to use the `converters/dosunix` port from the Ports Collection. Consult its documentation about the details.

9.14. How do I kill processes by name?

Use pkill(1).

9.15. How do I re-read `/etc/rc.conf` and re-start `/etc/rc` without a reboot?

Go into single user mode and then back to multi user mode.

On the console do:

    # shutdown now
    (Note: without -r or -h)

    # return
    # exit

9.16. I tried to update my system to the latest -STABLE, but got -BETA`x`, -RC or -PRERELEASE! What is going on?

Short answer: it is just a name. RC stands for “Release Candidate”. It signifies that a release is imminent. In FreeBSD, -PRERELEASE is typically synonymous with the code freeze before a release. (For some releases, the -BETA label was used in the same way as -PRERELEASE.)

Long answer: FreeBSD derives its releases from one of two places. Major, dot-zero, releases, such as 9.0-RELEASE are branched from the head of the development stream, commonly referred to as -CURRENT. Minor releases, such as 6.3-RELEASE or 5.2-RELEASE, have been snapshots of the active -STABLE branch. Starting with 4.3-RELEASE, each release also now has its own branch which can be tracked by people requiring an extremely conservative rate of development (typically only security advisories).

When a release is about to be made, the branch from which it will be derived from has to undergo a certain process. Part of this process is a code freeze. When a code freeze is initiated, the name of the branch is changed to reflect that it is about to become a release. For example, if the branch used to be called 6.2-STABLE, its name will be changed to 6.3-PRERELEASE to signify the code freeze and signify that extra pre-release testing should be happening. Bug fixes can still be committed to be part of the release. When the source code is in shape for the release the name will be changed to 6.3-RC to signify that a release is about to be made from it. Once in the RC stage, only the most critical bugs found can be fixed. Once the release (6.3-RELEASE in this example) and release branch have been made, the branch will be renamed to 6.3-STABLE.

For more information on version numbers and the various Subversion branches, refer to the Release Engineering article.

9.17. I tried to install a new kernel, and the chflags(1) failed. How do I get around this?

Short answer: You are probably at security level greater than 0. Reboot directly to Single User mode to install the kernel.

Long answer: FreeBSD disallows changing system flags at security levels greater than 0. You can check your security level with the command:

    # sysctl kern.securelevel

You cannot lower the security level; you have to boot to Single Mode to install the kernel, or change the security level in `/etc/rc.conf` then reboot. See the init(8) manual page for details on `securelevel`, and see `/etc/defaults/rc.conf` and the rc.conf(5) manual page for more information on `rc.conf`.

9.18. I cannot change the time on my system by more than one second! How do I get around this?

Short answer: You are probably at security level greater than 1. Reboot directly to Single User mode to change the date.

Long answer: FreeBSD disallows changing the time by more that one second at security levels greater than 1. You can check your security level with the command:

    # sysctl kern.securelevel

You cannot lower the security level; you have to boot to Single User mode to change the date, or change the security level in `/etc/rc.conf` then reboot. See the init(8) manual page for details on `securelevel`, and see `/etc/defaults/rc.conf` and the rc.conf(5) manual page for more information on `rc.conf`.

9.19. Why is `rpc.statd` using 256 MB of memory?

No, there is no memory leak, and it is not using 256 MB of memory. For convenience, `rpc.statd` maps an obscene amount of memory into its address space. There is nothing terribly wrong with this from a technical standpoint; it just throws off things like top(1) and ps(1).

rpc.statd(8) maps its status file (resident on `/var`) into its address space; to save worrying about remapping it later when it needs to grow, it maps it with a generous size. This is very evident from the source code, where one can see that the length argument to mmap(2) is `0x10000000`, or one sixteenth of the address space on an IA32, or exactly 256 MB.

9.20. Why can I not unset the `schg` file flag?

You are running at an elevated (i.e., greater than 0) securelevel. Lower the securelevel and try again. For more information, see the FAQ entry on securelevel and the init(8) manual page.

9.21. Why does SSH authentication through `.shosts` not work by default in recent versions of FreeBSD?

The reason why `.shosts` authentication does not work by default in more recent versions of FreeBSD is because ssh(1) is not installed suid `root` by default. To “fix” this, you can do one of the following:

- As a permanent fix, set `ENABLE_SUID_SSH` to `true` in `/etc/make.conf` then rebuild and reinstall ssh(1).

- As a temporary fix, change the mode on `/usr/bin/ssh` to `4555` by running `chmod 4555 /usr/bin/ssh` as `root`.

9.22. What is `vnlru`?

`vnlru` flushes and frees vnodes when the system hits the `kern.maxvnodes` limit. This kernel thread sits mostly idle, and only activates if you have a huge amount of RAM and are accessing tens of thousands of tiny files.

9.23. What do the various memory states displayed by `top` mean?

- `Active`: pages recently statistically used.

- `Inactive`: pages recently statistically unused.

- `Cache`: (most often) pages that have percolated from inactive to a status where they maintain their data, but can often be immediately reused (either with their old association, or reused with a new association). There can be certain immediate transitions from `active` to `cache` state if the page is known to be clean (unmodified), but that transition is a matter of policy, depending upon the algorithm choice of the VM system maintainer.

- `Free`: pages without data content, and can be immediately used in certain circumstances where cache pages might be ineligible. Free pages can be reused at interrupt or process state.

- `Wired`: pages that are fixed into memory, usually for kernel purposes, but also sometimes for special use in processes.

- Pages are most often written to disk (sort of a VM sync) when they are in the inactive state, but active pages can also be synced. This depends upon the CPU tracking of the modified bit being available, and in certain situations there can be an advantage for a block of VM pages to be synced, whether they are active or inactive. In most common cases, it is best to think of the inactive queue to be a queue of relatively unused pages that might or might not be in the process of being written to disk. Cached pages are already synced, not mapped, but available for immediate process use with their old association or with a new association. Free pages are available at interrupt level, but cached or free pages can be used at process state for reuse. Cache pages are not adequately locked to be available at interrupt level.

  There are some other flags (e.g., busy flag or busy count) that might modify some of the described rules.

9.24. How much free memory is available?

There are a couple of kinds of “free memory”. One kind is the amount of memory immediately available without paging anything else out. That is approximately the size of cache queue + size of free queue (with a derating factor, depending upon system tuning). Another kind of “free memory” is the total amount of VM space. That can be complex, but is dependent upon the amount of swap space and memory. Other kinds of “free memory” descriptions are also possible, but it is relatively useless to define these, but rather it is important to make sure that the paging rate is kept low, and to avoid running out of swap space.

9.25. What is `/var/empty`? I can not delete it!

`/var/empty` is a directory that the sshd(8) program uses when performing privilege separation. The `/var/empty` directory is empty, owned by `root` and has the `schg` flag set.

Although it is not recommended to delete this directory, to do so you will need to unset the `schg` flag first. See the chflags(1) manual page for more information (and bear in mind the answer to the question on unsetting the schg flag).

9.26. I just changed `/etc/newsyslog.conf`. How can I check if it does what I expect?

To see what newsyslog(8) will do use the following:

    % newsyslog -nrvv

9.27. My time is wrong, how can I change the timezone?

Use tzsetup(8).

# Chapter 10 The X Window System and Virtual Consoles

10.1. What is the X Window System?
10.2. I want to run Xorg, how do I go about it?
10.3. I tried to run X, but I get a “`No devices detected.`” error when I type `startx`. What do I do now?
10.4. Why does my mouse not work with X?
10.5. My mouse has a fancy wheel. Can I use it in X?
10.6. My laptop has a Synaptics touchpad. Can I use it in X?
10.7. How do I use remote X displays?
10.8. What is a virtual console and how do I make more?
10.9. How do I access the virtual consoles from X?
10.10. How do I start XDM on boot?
10.11. Why do I get “`Couldn't open console`” when I run `xconsole`?
10.12. Why does my PS/2 mouse misbehave under X?
10.13. How do I reverse the mouse buttons?
10.14. How do I install a splash screen and where do I find them?
10.15. Can I use the Windows keys on my keyboard in X?
10.16. How can I get 3D hardware acceleration for OpenGL®?

10.1. What is the X Window System?

The X Window System (commonly `X11`) is the most widely available windowing system capable of running on UNIX or UNIX like systems, including FreeBSD. The X.Org Foundation administers the X protocol standards, with the current reference implementation, version 11 release 7.5.2, so you will often see references shortened to `X11`.

Many implementations are available for different architectures and operating systems. An implementation of the server-side code is properly known as an `X server`.

10.2. I want to run Xorg, how do I go about it?

To install Xorg do one of the following:

Use the `x11/xorg` meta-port, which builds and installs every Xorg component.

Use `x11/xorg-minimal`, which builds and installs only the necessary Xorg components.

Install Xorg from FreeBSD packages:

    # pkg_add -r xorg

or on systems using pkg:

    # pkg install xorg

After the installation of Xorg, follow the instructions from the X11 Configuration section of the FreeBSD Handbook.

10.3. I tried to run X, but I get a “`No devices detected.`” error when I type `startx`. What do I do now?

Your system is probably running at a raised `securelevel`. It is not possible to start X at a raised `securelevel` because X requires write access to io(4). For more information, see at the init(8) manual page.

There are two solutions to the problem: Set your `securelevel` back down to zero (usually in `/etc/rc.conf`), or run xdm(1) (or an alternative display manager) at boot time (before the `securelevel` is raised).

See Q: 10.10. for more information about running xdm(1) at boot time.

10.4. Why does my mouse not work with X?

If you are using syscons(4) (the default console driver), you can configure FreeBSD to support a mouse pointer on each virtual screen. To avoid conflicting with X, syscons(4) supports a virtual device called `/dev/sysmouse`. All mouse events received from the real mouse device are written to the sysmouse(4) device via moused(8). To use your mouse on one or more virtual consoles, and use X, see Q: 4.4.1. and set up moused(8).

Then edit `/etc/X11/xorg.conf` and make sure you have the following lines:

    Section "InputDevice"
       Option          "Protocol" "SysMouse"
       Option          "Device" "/dev/sysmouse"
    .....

Starting with Xorg version 7.4, the `InputDevice` sections in `xorg.conf` are ignored in favor of autodetected devices. To restore the old behavior, add the following line to the `ServerLayout` or `ServerFlags` section:

    Option "AutoAddDevices" "false"

Some people prefer to use `/dev/mouse` under X. To make this work, `/dev/mouse` should be linked to `/dev/sysmouse` (see sysmouse(4)) by adding the following line to `/etc/devfs.conf` (see devfs.conf(5)):

    link    sysmouse    mouse

This link can be created by restarting devfs(5) with the following command (as `root`):

    # service devfs restart

10.5. My mouse has a fancy wheel. Can I use it in X?

Yes.

You need to tell X that you have a 5 button mouse. To do this, simply add the lines `Buttons 5` and `ZAxisMapping 4 5` to the “InputDevice” section of `/etc/X11/xorg.conf`. For example, you might have the following “InputDevice” section in `/etc/X11/xorg.conf`.

Example 10-1. “InputDevice” Section for Wheeled Mouse in Xorg Configuration File

    Section "InputDevice"
       Identifier      "Mouse1"
       Driver          "mouse"
       Option          "Protocol" "auto"
       Option          "Device" "/dev/sysmouse"
       Option          "Buttons" "5"
       Option          "ZAxisMapping" "4 5"
    EndSection

Example 10-2. “.emacs” Example for Naive Page Scrolling with Wheeled Mouse (optional)

    ;; wheel mouse
    (global-set-key [mouse-4] 'scroll-down)
    (global-set-key [mouse-5] 'scroll-up)

10.6. My laptop has a Synaptics touchpad. Can I use it in X?

Yes, you will have to configure a few things to make it work.

If you plan to use the Xorg synaptics driver you must remove moused_enable from `rc.conf`. Xorg can not use the synaptics mouse if the moused already sits on `/dev/psm0`.

To enable synaptics in the psm(4) driver you need to add the following into `/boot/loader.conf`:

    hw.psm.synaptics_support="1"

You also need the following into `xorg.conf`:

    Section "InputDevice"
    Identifier  "Touchpad0"
    Driver      "synaptics"
    Option      "Protocol" "psm"
    Option      "Device" "/dev/psm0"
    EndSection

And be sure to add the following into the “ServerLayout” section:

    InputDevice    "Touchpad0" "SendCoreEvents"

10.7. How do I use remote X displays?

For security reasons, the default setting is to not allow a machine to remotely open a window.

To enable this feature, simply start X with the optional `-listen_tcp` argument:

    % startx -listen_tcp

10.8. What is a virtual console and how do I make more?

Virtual consoles, put simply, enable you to have several simultaneous sessions on the same machine without doing anything complicated like setting up a network or running X.

When the system starts, it will display a login prompt on the monitor after displaying all the boot messages. You can then type in your login name and password and start working (or playing!) on the first virtual console.

At some point, you will probably wish to start another session, perhaps to look at documentation for a program you are running or to read your mail while waiting for an FTP transfer to finish. Just do Alt+F2 (hold down Alt and press F2), and you will find a login prompt waiting for you on the second “virtual console”! When you want to go back to the original session, do Alt+F1.

The default FreeBSD installation has eight virtual consoles enabled. Alt+F1, Alt+F2, Alt+F3, and so on will switch between these virtual consoles.

To enable more of them, edit `/etc/ttys` (see ttys(5)) and add entries for `ttyv8` to `ttyvc` after the comment on “Virtual terminals”:

    # Edit the existing entry for ttyv8 in /etc/ttys and change
    # "off" to "on".
    ttyv8   "/usr/libexec/getty Pc"         xterm  on secure
    ttyv9   "/usr/libexec/getty Pc"         xterm  on secure
    ttyva   "/usr/libexec/getty Pc"         xterm  on secure
    ttyvb   "/usr/libexec/getty Pc"         xterm  on secure

Use as many or as few as you want. The more virtual terminals you have, the more resources that are used; this can be important if you have 8 MB RAM or less. You may also want to change the `secure` to `insecure`.

> Note: Versions of FreeBSD prior to 9.0 used the “ cons25” terminal type, and not “ xterm”. Existing entries in `/etc/ttys` can be used on which to base new additions.

> Important: If you want to run an X server you must leave at least one virtual terminal unused (or turned off) for it to use. That is to say that if you want to have a login prompt pop up for all twelve of your Alt-function keys, you are out of luck — you can only do this for eleven of them if you also want to run an X server on the same machine.

The easiest way to disable a console is by turning it off. For example, if you had the full 12 terminal allocation mentioned above and you wanted to run X, you would change settings for virtual terminal 12 from:

    ttyvb   "/usr/libexec/getty Pc"         xterm  on  secure

to:

    ttyvb   "/usr/libexec/getty Pc"         xterm  off secure

If your keyboard has only ten function keys, you would end up with:

    ttyv9   "/usr/libexec/getty Pc"         xterm  off secure
    ttyva   "/usr/libexec/getty Pc"         xterm  off secure
    ttyvb   "/usr/libexec/getty Pc"         xterm  off secure

(You could also just delete these lines.)

Next, the easiest (and cleanest) way to activate the virtual consoles is to reboot. However, if you really do not want to reboot, you can just shut down the X Window system and execute (as `root`):

    # kill -HUP 1

It is imperative that you completely shut down X Window if it is running, before running this command. If you do not, your system will probably appear to hang or lock up after executing `kill`.

10.9. How do I access the virtual consoles from X?

Use Ctrl+Alt+F`n` to switch back to a virtual console. Ctrl+Alt+F1 would return you to the first virtual console.

Once you are back to a text console, you can then use Alt+F`n` as normal to move between them.

To return to the X session, you must switch to the virtual console running X. If you invoked X from the command line, (e.g., using `startx`) then the X session will attach to the next unused virtual console, not the text console from which it was invoked. If you have eight active virtual terminals then X will be running on the ninth, and you would use Alt+F9 to return.

10.10. How do I start XDM on boot?

There are two schools of thought on how to start xdm(1). One school starts `xdm` from `/etc/ttys` (see ttys(5)) using the supplied example, while the other simply runs `xdm` from `rc.local` (see rc(8)) or from an `X` script in `/usr/local/etc/rc.d`. Both are equally valid, and one may work in situations where the other does not. In both cases the result is the same: X will pop up a graphical login prompt.

The ttys(5) method has the advantage of documenting which vty X will start on and passing the responsibility of restarting the X server on logout to init(8). The rc(8) method makes it easy to `kill` `xdm` if there is a problem starting the X server.

If loaded from rc(8), `xdm` should be started without any arguments (i.e., as a daemon). `xdm` must start after getty(8) runs, or else `getty` and `xdm` will conflict, locking out the console. The best way around this is to have the script sleep 10 seconds or so then launch `xdm`.

If you are to start `xdm` from `/etc/ttys`, there still is a chance of conflict between `xdm` and getty(8). One way to avoid this is to add the `vt` number in `/usr/local/lib/X11/xdm/Xservers`

    :0 local /usr/local/bin/X vt4

The above example will direct the X server to run in `/dev/ttyv3`. Note the number is offset by one. The X server counts the vty from one, whereas the FreeBSD kernel numbers the vty from zero.

10.11. Why do I get “`Couldn't open console`” when I run `xconsole`?

If you start X with `startx`, the permissions on `/dev/console` will not get changed, resulting in things like `xterm -C` and `xconsole` not working.

This is because of the way console permissions are set by default. On a multi-user system, one does not necessarily want just any user to be able to write on the system console. For users who are logging directly onto a machine with a VTY, the fbtab(5) file exists to solve such problems.

In a nutshell, make sure an uncommented line of the form is in `/etc/fbtab` (see fbtab(5)):

    /dev/ttyv0 0600 /dev/console

It will ensure that whomever logs in on `/dev/ttyv0` will own the console.

10.12. Why does my PS/2 mouse misbehave under X?

Your mouse and the mouse driver may have somewhat become out of synchronization.

In rare cases the driver may erroneously report synchronization problem and you may see the kernel message:

    psmintr: out of sync (xxxx != yyyy)

and notice that your mouse does not work properly.

If this happens, disable the synchronization check code by setting the driver flags for the PS/2 mouse driver to `0x100`. This can be easiest achieved by adding

    hint.psm.0.flags="0x100"

to `/boot/loader.conf` and rebooting.

10.13. How do I reverse the mouse buttons?

Run the command `xmodmap -e "pointer = 3 2 1"` from `.xinitrc` or `.xsession`.

10.14. How do I install a splash screen and where do I find them?

The detailed answer for this question can be found in the Boot Time Splash Screens section of the FreeBSD Handbook.

10.15. Can I use the Windows keys on my keyboard in X?

Yes. All you need to do is use xmodmap(1) to define what function you wish them to perform.

Assuming all “Windows” keyboards are standard then the keycodes for these three keys are the following:

- 115 — Windows key, between the left-hand Ctrl and Alt keys

- 116 — Windows key, to the right of AltGr

- 117 — Menu, to the left of the right-hand Ctrl

To have the left Windows key print a comma, try this.

    # xmodmap -e "keycode 115 = comma"

To have the Windows key-mappings enabled automatically every time you start X either put the `xmodmap` commands in `~/.xinitrc` or, preferably, create a `~/.xmodmaprc` and include the `xmodmap` options, one per line, then add the following line to `~/.xinitrc`:

    xmodmap $HOME/.xmodmaprc

For example, you could map the 3 keys to be F13, F14, and F15, respectively. This would make it easy to map them to useful functions within applications or your window manager, as demonstrated further down.

To do this put the following in `~/.xmodmaprc`.

    keycode 115 = F13
    keycode 116 = F14
    keycode 117 = F15

If you use the `x11-wm/fvwm2` port, for example, you could map the keys so that F13 iconifies (or de-iconifies) the window the cursor is in, F14 brings the window the cursor is in to the front or, if it is already at the front, pushes it to the back, and F15 pops up the main Workplace (application) menu even if the cursor is not on the desktop, which is useful if you do not have any part of the desktop visible (and the logo on the key matches its functionality).

The following entries in `~/.fvwmrc` implement the aforementioned setup:

    Key F13        FTIWS    A        Iconify
    Key F14        FTIWS    A        RaiseLower
    Key F15        A        A        Menu Workplace Nop

10.16. How can I get 3D hardware acceleration for OpenGL®?

The availability of 3D acceleration depends on the version of Xorg that you are using and the type of video chip you have. If you have an nVidia chip, you can use the binary drivers provided for FreeBSD by installing one of the following ports:

- The latest versions of nVidia cards are supported by the `x11/nvidia-driver` port.

- nVidia cards like the GeForce2 MX/3/4 series are supported by the 96XX series of drivers, available in the `x11/nvidia-driver-96xx` port.

- Even older cards, like GeForce and RIVA TNT are supported by the 71XX series of drivers, available in the `x11/nvidia-driver-71xx` port.

nVidia provides detailed information on which card is supported by which driver on their web site: http://www.nvidia.com/object/IO_32667.html.

For Matrox G200/G400, check the `x11-servers/mga_hal` port.

For ATI Rage 128 and Radeon see ati(4), r128(4) and radeon(4).

# Chapter 11 Networking

11.1. Where can I get information on “diskless booting”?
11.2. Can a FreeBSD box be used as a dedicated network router?
11.3. Can I connect my Windows box to the Internet via FreeBSD?
11.4. Does FreeBSD support PPP?
11.5. Does FreeBSD support NAT or Masquerading?
11.6. How can I set up Ethernet aliases?
11.7. Why can I not NFS-mount from a Linux box?
11.8. Why does `mountd` keep telling me it “`can't change attributes`” and that I have a “`bad exports list`” on my FreeBSD NFS server?
11.9. How do I enable IP multicast support?
11.10. Why do I have to use the FQDN for hosts on my site?
11.11. Why do I get an error, “`Permission denied`”, for all networking operations?
11.12. Why is my `ipfw` “fwd” rule to redirect a service to another machine not working?
11.13. How can I redirect service requests from one machine to another?
11.14. Where can I get a bandwidth management tool?
11.15. Why do I get “`/dev/bpf0: device not configured`”?
11.16. How do I mount a disk from a Windows machine that is on my network, like smbmount in Linux?
11.17. What are these messages about: “`Limiting icmp/open port/closed port response`” in my log files?
11.18. What are these “`arp: unknown hardware address format`” error messages?
11.19. Why do I keep seeing messages like: “`192.168.0.10 is on fxp1 but got reply from 00:15:17:67:cf:82 on rl0`”, and how do I disable it?

11.1. Where can I get information on “diskless booting”?

“Diskless booting” means that the FreeBSD box is booted over a network, and reads the necessary files from a server instead of its hard disk. For full details, please read the Handbook entry on diskless booting.

11.2. Can a FreeBSD box be used as a dedicated network router?

Yes. Please see the Handbook entry on advanced networking, specifically the section on routing and gateways.

11.3. Can I connect my Windows box to the Internet via FreeBSD?

Typically, people who ask this question have two PCs at home, one with FreeBSD and one with some version of Windows the idea is to use the FreeBSD box to connect to the Internet and then be able to access the Internet from the Windows box through the FreeBSD box. This is really just a special case of the previous question and works perfectly well.

Dialup users must use `-nat` and set `gateway_enable` to YES in `/etc/rc.conf`. For more information, please see the ppp(8) manual page or the Handbook entry on user PPP.

If you are using kernel-mode PPP or have an Ethernet connection to the Internet, you need to use natd(8). Please look at the natd section of the Handbook for a tutorial.

11.4. Does FreeBSD support PPP?

Yes. ppp(8) provides support for both incoming and outgoing connections.

For more information on how to use this, please see the Handbook chapter on PPP.

11.5. Does FreeBSD support NAT or Masquerading?

Yes. If you want to use NAT over a user PPP connection, please see the Handbook entry on user PPP. If you want to use NAT over some other sort of network connection, please look at the natd section of the Handbook.

11.6. How can I set up Ethernet aliases?

If the alias is on the same subnet as an address already configured on the interface, then add `netmask 0xffffffff` to your ifconfig(8) command-line, as in the following:

    # ifconfig ed0 alias 192.0.2.2 netmask 0xffffffff

Otherwise, just specify the network address and netmask as usual:

    # ifconfig ed0 alias 172.16.141.5 netmask 0xffffff00

You can read more about this in the FreeBSD Handbook.

11.7. Why can I not NFS-mount from a Linux box?

Some versions of the Linux NFS code only accept mount requests from a privileged port; try to issue the following command:

    # mount -o -P linuxbox:/blah /mnt

11.8. Why does `mountd` keep telling me it “`can't change attributes`” and that I have a “`bad exports list`” on my FreeBSD NFS server?

The most frequent problem is not understanding the correct format of `/etc/exports`. Please review exports(5) and the NFS entry in the Handbook, especially the section on configuring NFS.

11.9. How do I enable IP multicast support?

FreeBSD supports multicast host operations by default. If you want your box to run as a multicast router, you need to recompile your kernel with the `MROUTING` option and run mrouted(8). FreeBSD will start mrouted(8) at boot time if the flag `mrouted_enable` is set to `YES` in `/etc/rc.conf`.

> Note: In recent FreeBSD releases, the mrouted(8) multicast routing daemon, the map-mbone(8) and mrinfo(8) utilities have been removed from the base system. These programs are now available in the FreeBSD Ports Collection as `net/mrouted`.

11.10. Why do I have to use the FQDN for hosts on my site?

See the answer in the FreeBSD Handbook.

11.11. Why do I get an error, “`Permission denied`”, for all networking operations?

If you have compiled your kernel with the `IPFIREWALL` option, you need to be aware that the default policy is to deny all packets that are not explicitly allowed.

If you had unintentionally misconfigured your system for firewalling, you can restore network operability by typing the following while logged in as `root`:

    # ipfw add 65534 allow all from any to any

You can also set `firewall_type="open"` in `/etc/rc.conf`.

For further information on configuring a FreeBSD firewall, see the Handbook chapter.

11.12. Why is my `ipfw` “fwd” rule to redirect a service to another machine not working?

Possibly because you want to do network address translation (NAT) and not just forward packets. A “fwd” rule does exactly what it says; it forwards packets. It does not actually change the data inside the packet. Say we have a rule like:

    01000 fwd 10.0.0.1 from any to foo 21

When a packet with a destination address of `foo` arrives at the machine with this rule, the packet is forwarded to `10.0.0.1`, but it still has the destination address of `foo`! The destination address of the packet is not changed to `10.0.0.1`. Most machines would probably drop a packet that they receive with a destination address that is not their own. Therefore, using a “fwd” rule does not often work the way the user expects. This behavior is a feature and not a bug.

See the FAQ about redirecting services, the natd(8) manual, or one of the several port redirecting utilities in the Ports Collection for a correct way to do this.

11.13. How can I redirect service requests from one machine to another?

You can redirect FTP (and other service) request with the `sysutils/socket` port. Simply replace the service's command line to call `socket` instead, like so:

    ftp stream tcp nowait nobody /usr/local/bin/socket socket ftp.example.com ftp

where `ftp.example.com` and `ftp` are the host and port to redirect to, respectively.

11.14. Where can I get a bandwidth management tool?

There are three bandwidth management tools available for FreeBSD. dummynet(4) is integrated into FreeBSD as part of ipfw(4). ALTQ has been integrated into FreeBSD as part of pf(4). Bandwidth Manager from Emerging Technologies is a commercial product.

11.15. Why do I get “`/dev/bpf0: device not configured`”?

You are running a program that requires the Berkeley Packet Filter (bpf(4)), but it is not in your kernel. Add this to your kernel config file and build a new kernel:

    device bpf        # Berkeley Packet Filter

11.16. How do I mount a disk from a Windows machine that is on my network, like smbmount in Linux?

Use the SMBFS toolset. It includes a set of kernel modifications and a set of userland programs. The programs and information are available as mount_smbfs(8) in the base system.

11.17. What are these messages about: “`Limiting icmp/open port/closed port response`” in my log files?

This is the kernel telling you that some activity is provoking it to send more ICMP or TCP reset (RST) responses than it thinks it should. ICMP responses are often generated as a result of attempted connections to unused UDP ports. TCP resets are generated as a result of attempted connections to unopened TCP ports. Among others, these are the kinds of activities which may cause these messages:

- Brute-force denial of service (DoS) attacks (as opposed to single-packet attacks which exploit a specific vulnerability).

- Port scans which attempt to connect to a large number of ports (as opposed to only trying a few well-known ports).

The first number in the message tells you how many packets the kernel would have sent if the limit was not in place, and the second number tells you the limit. You can control the limit using the `net.inet.icmp.icmplim` sysctl variable like this, where `300` is the limit in packets per second:

    # sysctl net.inet.icmp.icmplim=300

If you do not want to see messages about this in your log files, but you still want the kernel to do response limiting, you can use the `net.inet.icmp.icmplim_output` sysctl variable to disable the output like this:

    # sysctl net.inet.icmp.icmplim_output=0

Finally, if you want to disable response limiting, you can set the `net.inet.icmp.icmplim` sysctl variable (see above for an example) to `0`. Disabling response limiting is discouraged for the reasons listed above.

11.18. What are these “`arp: unknown hardware address format`” error messages?

This means that some device on your local Ethernet is using a MAC address in a format that FreeBSD does not recognize. This is probably caused by someone experimenting with an Ethernet card somewhere else on the network. You will see this most commonly on cable modem networks. It is harmless, and should not affect the performance of your FreeBSD machine.

11.19. Why do I keep seeing messages like: “`192.168.0.10 is on fxp1 but got reply from 00:15:17:67:cf:82 on rl0`”, and how do I disable it?

Because a packet is coming from outside the network unexpectedly. To disable them, set `net.link.ether.inet.log_arp_wrong_iface` to `0`.

# Chapter 12 Security

12.1. What is a sandbox?
12.2. What is securelevel?
12.3. BIND (`named`) is listening on some high-numbered ports. What is going on?
12.4. The sendmail daemon is listening on port 587 as well as the standard port 25! What is going on?
12.5. What is this UID 0 `toor` account? Have I been compromised?

12.1. What is a sandbox?

“Sandbox” is a security term. It can mean two things:

- A process which is placed inside a set of virtual walls that are designed to prevent someone who breaks into the process from being able to break into the wider system.

  The process is said to be able to “play” inside the walls. That is, nothing the process does in regards to executing code is supposed to be able to breech the walls so you do not have to do a detailed audit of its code to be able to say certain things about its security.

  The walls might be a user ID, for example. This is the definition used in the security(7) and named(8) man pages.

  Take the `ntalk` service, for example (see inetd(8)). This service used to run as user ID `root`. Now it runs as user ID `tty`. The `tty` user is a sandbox designed to make it more difficult for someone who has successfully hacked into the system via `ntalk` from being able to hack beyond that user ID.

- A process which is placed inside a simulation of the machine. It means that someone who is able to break into the process may believe that he can break into the wider machine but is, in fact, only breaking into a simulation of that machine and not modifying any real data.

  The most common way to accomplish this is to build a simulated environment in a subdirectory and then run the processes in that directory chrooted (i.e., `/` for that process is this directory, not the real `/` of the system).

  Another common use is to mount an underlying file system read-only and then create a file system layer on top of it that gives a process a seemingly writeable view into that file system. The process may believe it is able to write to those files, but only the process sees the effects — other processes in the system do not, necessarily.

  An attempt is made to make this sort of sandbox so transparent that the user (or hacker) does not realize that he is sitting in it.

UNIX implements two core sandboxes. One is at the process level, and one is at the userid level.

Every UNIX process is completely firewalled off from every other UNIX process. One process cannot modify the address space of another.

A UNIX process is owned by a particular userid. If the user ID is not the `root` user, it serves to firewall the process off from processes owned by other users. The user ID is also used to firewall off on-disk data.

12.2. What is securelevel?

`securelevel` is a security mechanism implemented in the kernel. When the securelevel is positive, the kernel restricts certain tasks; not even the superuser (i.e., `root`) is allowed to do them. The securelevel mechanism limits the ability to:

- Unset certain file flags, such as `schg` (the system immutable flag).

- Write to kernel memory via `/dev/mem` and `/dev/kmem`.

- Load kernel modules.

- Alter firewall rules.

To check the status of the securelevel on a running system, simply execute the following command:

    # sysctl -n kern.securelevel

The output contains the current value of the securelevel. If it is positive (i.e., greater than 0), at least some of the securelevel's protections are enabled.

The securelevel of a running system can not be lowered as this would defeat its purpose. If you need to do a task that requires that the securelevel be non-positive (e.g., an `installworld` or changing the date), you will have to change the securelevel setting in `/etc/rc.conf` (you want to look for the `kern_securelevel` and `kern_securelevel_enable` variables) and reboot.

For more information on securelevel and the specific things all the levels do, please consult the init(8) manual page.

> Warning: Securelevel is not a silver bullet; it has many known deficiencies. More often than not, it provides a false sense of security.

> One of its biggest problems is that in order for it to be at all effective, all files used in the boot process up until the securelevel is set must be protected. If an attacker can get the system to execute their code prior to the securelevel being set (which happens quite late in the boot process since some things the system must do at start-up cannot be done at an elevated securelevel), its protections are invalidated. While this task of protecting all files used in the boot process is not technically impossible, if it is achieved, system maintenance will become a nightmare since one would have to take the system down, at least to single-user mode, to modify a configuration file.

> This point and others are often discussed on the mailing lists, particularly the FreeBSD security mailing list. Please search the archives here for an extensive discussion. A more fine-grained mechanism is preferred.

12.3. BIND (`named`) is listening on some high-numbered ports. What is going on?

BIND uses a random high-numbered port for outgoing queries. Recent versions of it choose a new, random UDP port for each query. This may cause problems for some network configurations, especially if a firewall blocks incoming UDP packets on particular ports. If you want to get past that firewall, you can try the `avoid-v4-udp-ports` and `avoid-v6-udp-ports` options to avoid selecting random port numbers within a blocked range.

> Warning: If a port number (like 53) is specified via the `query-source` or `query-source-v6` options in `/etc/namedb/named.conf`, randomized port selection will not be used. It is strongly recommended that these options not be used to specify fixed port numbers.

Congratulations, by the way. It is good practice to read your sockstat(1) output and notice odd things!

12.4. The sendmail daemon is listening on port 587 as well as the standard port 25! What is going on?

Recent versions of sendmail support a mail submission feature that runs over port 587. This is not yet widely supported, but is growing in popularity.

12.5. What is this UID 0 `toor` account? Have I been compromised?

Do not worry. `toor` is an “alternative” superuser account (toor is root spelt backwards). Previously it was created when the bash(1) shell was installed but now it is created by default. It is intended to be used with a non-standard shell so you do not have to change `root`'s default shell. This is important as shells which are not part of the base distribution (for example a shell installed from ports or packages) are likely to be installed in `/usr/local/bin` which, by default, resides on a different file system. If `root`'s shell is located in `/usr/local/bin` and `/usr` (or whatever file system contains `/usr/local/bin`) is not mounted for some reason, `root` will not be able to log in to fix a problem (although if you reboot into single user mode you will be prompted for the path to a shell).

Some people use `toor` for day-to-day `root` tasks with a non-standard shell, leaving `root`, with a standard shell, for single user mode or emergencies. By default you cannot log in using `toor` as it does not have a password, so log in as `root` and set a password for `toor` if you want to use it.

# Chapter 13 PPP

13.1. I cannot make ppp(8) work. What am I doing wrong?
13.2. Why does ppp(8) hang when I run it?
13.3. Why will ppp(8) not dial in `-auto` mode?
13.4. What does “`No route to host`” mean?
13.5. Why does my connection drop after about 3 minutes?
13.6. Why does my connection drop under heavy load?
13.7. Why does my connection drop after a random amount of time?
13.8. Why does my connection hang after a random amount of time?
13.9. The remote end is not responding. What can I do?
13.10. ppp(8) has hung. What can I do?
13.11. I keep seeing errors about magic being the same. What does it mean?
13.12. LCP negotiations continue until the connection is closed. What is wrong?
13.13. Why does ppp(8) lock up when I shell out to test it?
13.14. Why does ppp(8) over a null-modem cable never exit?
13.15. Why does ppp(8) dial for no reason in `-auto` mode?
13.16. What do these CCP errors mean?
13.17. Why does ppp(8) not log my connection speed?
13.18. Why does ppp(8) ignore the `\` character in my chat script?
13.19. Why does ppp(8) get a “`Segmentation fault`”, but I see no `ppp.core`
13.20. Why does the process that forces a dial in `-auto` mode never connect?
13.21. Why do most games not work with the `-nat` switch?
13.22. What are FCS errors?
13.23. None of this helps — I am desperate! What can I do?

13.1. I cannot make ppp(8) work. What am I doing wrong?

You should first read the ppp(8) manual page and the PPP section of the handbook. Enable logging with the following command:

    set log Phase Chat Connect Carrier lcp ipcp ccp command

This command may be typed at the ppp(8) command prompt or it may be entered in the `/etc/ppp/ppp.conf` configuration file (the start of the `default` section is the best place to put it). Make sure that `/etc/syslog.conf` (see syslog.conf(5)) contains the lines below and the file `/var/log/ppp.log` exists:

    !ppp
    *.*        /var/log/ppp.log

You can now find out a lot about what is going on from the log file. Do not worry if it does not all make sense. If you need to get help from someone, it may make sense to them.

13.2. Why does ppp(8) hang when I run it?

This is usually because your hostname will not resolve. The best way to fix this is to make sure that `/etc/hosts` is consulted by your resolver first by editing `/etc/host.conf` and putting the `hosts` line first. Then, simply put an entry in `/etc/hosts` for your local machine. If you have no local network, change your `localhost` line:

    127.0.0.1        foo.example.com foo localhost

Otherwise, simply add another entry for your host. Consult the relevant manual pages for more details.

You should be able to successfully `ping -c1 `hostname`` when you are done.

13.3. Why will ppp(8) not dial in `-auto` mode?

First, check that you have got a default route. By running `netstat -rn` (see netstat(1)), you should see two entries like this:

    Destination        Gateway            Flags     Refs     Use     Netif Expire
    default            10.0.0.2           UGSc        0        0      tun0
    10.0.0.2           10.0.0.1           UH          0        0      tun0

This is assuming that you have used the addresses from the handbook, the manual page, or from `ppp.conf.sample`. If you do not have a default route, it may be because you forgot to add the `HISADDR` line to `ppp.conf`.

Another reason for the default route line being missing is that you have mistakenly set up a default router in your `/etc/rc.conf` (see rc.conf(5)) file and you have omitted the line below from `ppp.conf`:

    delete ALL

If this is the case, go back to the Final System Configuration section of the handbook.

13.4. What does “`No route to host`” mean?

This error is usually due that the following section is missing in your `/etc/ppp/ppp.linkup`:

    MYADDR:
      delete ALL
      add 0 0 HISADDR

This is only necessary if you have a dynamic IP address or do not know the address of your gateway. If you are using interactive mode, you can type the following after entering `packet mode` (packet mode is indicated by the capitalized PPP in the prompt):

    delete ALL
    add 0 0 HISADDR

Refer to the PPP and Dynamic IP addresses section of the handbook for further details.

13.5. Why does my connection drop after about 3 minutes?

The default PPP timeout is 3 minutes. This can be adjusted with the following line:

    set timeout NNN

where `NNN` is the number of seconds of inactivity before the connection is closed. If `NNN` is zero, the connection is never closed due to a timeout. It is possible to put this command in `ppp.conf`, or to type it at the prompt in interactive mode. It is also possible to adjust it on the fly while the line is active by connecting to ppp's server socket using telnet(1) or pppctl(8). Refer to the ppp(8) man page for further details.

13.6. Why does my connection drop under heavy load?

If you have Link Quality Reporting (LQR) configured, it is possible that too many LQR packets are lost between your machine and the peer. ppp(8) deduces that the line must therefore be bad, and disconnects. LQR is disabled by default and can be enabled with the following line:

    enable lqr

13.7. Why does my connection drop after a random amount of time?

Sometimes, on a noisy phone line or even on a line with call waiting enabled, your modem may hang up because it thinks (incorrectly) that it lost carrier.

There is a setting on most modems for determining how tolerant it should be to temporary losses of carrier. Refer to the modem manual for details.

13.8. Why does my connection hang after a random amount of time?

Many people experience hung connections with no apparent explanation. The first thing to establish is which side of the link is hung.

If you are using an external modem, you can simply try using ping(8) to see if the TD light is flashing when you transmit data. If it flashes (and the RD light does not), the problem is with the remote end. If TD does not flash, the problem is local. With an internal modem, you will need to use the `set server` command in `ppp.conf`. When the hang occurs, connect to ppp(8) using pppctl(8). If your network connection suddenly revives (PPP was revived due to the activity on the diagnostic socket) or if you cannot connect (assuming the `set socket` command succeeded at startup time), the problem is local. If you can connect and things are still hung, enable local async logging with `set log local async` and use ping(8) from another window or terminal to make use of the link. The async logging will show you the data being transmitted and received on the link. If data is going out and not coming back, the problem is remote.

Having established whether the problem is local or remote, you now have two possibilities:

- If the problem is remote, read on entry Q: 13.9..

- If the problem is local, read on entry Q: 13.10..

13.9. The remote end is not responding. What can I do?

There is very little you can do about this. Most ISPs will refuse to help if you are not running a Microsoft® OS. You can `enable lqr` in your `ppp.conf`, allowing ppp(8) to detect the remote failure and hang up, but this detection is relatively slow and therefore not that useful. You may want to avoid telling your ISP that you are running user-PPP.

First, try disabling all local compression by adding the following to your configuration:

    disable pred1 deflate deflate24 protocomp acfcomp shortseq vj
    deny pred1 deflate deflate24 protocomp acfcomp shortseq vj

Then reconnect to ensure that this makes no difference. If things improve or if the problem is solved completely, determine which setting makes the difference through trial and error. This will provide good ammunition when you contact your ISP (although it may make it apparent that you are not running a Microsoft product).

Before contacting your ISP, enable async logging locally and wait until the connection hangs again. This may use up quite a bit of disk space. The last data read from the port may be of interest. It is usually ASCII data, and may even describe the problem (“`Memory fault`”, “`Core dumped`”).

If your ISP is helpful, they should be able to enable logging on their end, then when the next link drop occurs, they may be able to tell you why their side is having a problem.

13.10. ppp(8) has hung. What can I do?

Your best bet here is to rebuild ppp(8) with debugging information, and then use gdb(1) to grab a stack trace from the ppp process that is stuck. To rebuild the ppp utility with debugging information, you can type:

    # cd /usr/src/usr.sbin/ppp
    # env DEBUG_FLAGS='-g' make clean
    # env DEBUG_FLAGS='-g' make install

Then you should restart ppp and wait until it hangs again. When the debug build of ppp hangs, start gdb on the stuck process by typing:

    # gdb ppp `pgrep ppp`

At the gdb prompt, you can use the `bt` or `where` commands to get a stack trace. Save the output of your gdb session, and “detach” from the running process by typing `quit`.

13.11. I keep seeing errors about magic being the same. What does it mean?

Occasionally, just after connecting, you may see messages in the log that say “`Magic is same`”. Sometimes, these messages are harmless, and sometimes one side or the other exits. Most PPP implementations cannot survive this problem, and even if the link seems to come up, you will see repeated configure requests and configure acknowledgments in the log file until ppp(8) eventually gives up and closes the connection.

This normally happens on server machines with slow disks that are spawning a getty(8) on the port, and executing ppp(8) from a login script or program after login. There were reports of it happening consistently when using slirp. The reason is that in the time taken between getty(8) exiting and ppp(8) starting, the client-side ppp(8) starts sending Line Control Protocol (LCP) packets. Because ECHO is still switched on for the port on the server, the client ppp(8) sees these packets “reflect” back.

One part of the LCP negotiation is to establish a magic number for each side of the link so that “reflections” can be detected. The protocol says that when the peer tries to negotiate the same magic number, a NAK should be sent and a new magic number should be chosen. During the period that the server port has ECHO turned on, the client ppp(8) sends LCP packets, sees the same magic in the reflected packet and NAKs it. It also sees the NAK reflect (which also means ppp(8) must change its magic). This produces a potentially enormous number of magic number changes, all of which are happily piling into the server's tty buffer. As soon as ppp(8) starts on the server, it is flooded with magic number changes and almost immediately decides it has tried enough to negotiate LCP and gives up. Meanwhile, the client, who no longer sees the reflections, becomes happy just in time to see a hangup from the server.

This can be avoided by allowing the peer to start negotiating with the following line in `ppp.conf`:

    set openmode passive

This tells ppp(8) to wait for the server to initiate LCP negotiations. Some servers however may never initiate negotiations. If this is the case, you can do something like:

    set openmode active 3

This tells ppp(8) to be passive for 3 seconds, and then to start sending LCP requests. If the peer starts sending requests during this period, ppp(8) will immediately respond rather than waiting for the full 3 second period.

13.12. LCP negotiations continue until the connection is closed. What is wrong?

There is currently an implementation mis-feature in ppp(8) where it does not associate LCP, CCP & IPCP responses with their original requests. As a result, if one PPP implementation is more than 6 seconds slower than the other side, the other side will send two additional LCP configuration requests. This is fatal.

Consider two implementations, `A` and `B`. `A` starts sending LCP requests immediately after connecting and `B` takes 7 seconds to start. When `B` starts, `A` has sent 3 LCP REQs. We are assuming the line has ECHO switched off, otherwise we would see magic number problems as described in the previous section. `B` sends a REQ, then an ACK to the first of `A`'s REQs. This results in `A` entering the OPENED state and sending and ACK (the first) back to `B`. In the meantime, `B` sends back two more ACKs in response to the two additional REQs sent by `A` before `B` started up. `B` then receives the first ACK from `A` and enters the OPENED state. `A` receives the second ACK from `B` and goes back to the REQ-SENT state, sending another (forth) REQ as per the RFC. It then receives the third ACK and enters the OPENED state. In the meantime, `B` receives the forth REQ from `A`, resulting in it reverting to the ACK-SENT state and sending another (second) REQ and (forth) ACK as per the RFC. `A` gets the REQ, goes into REQ-SENT and sends another REQ. It immediately receives the following ACK and enters OPENED.

This goes on until one side figures out that they are getting nowhere and gives up.

The best way to avoid this is to configure one side to be `passive` — that is, make one side wait for the other to start negotiating. This can be done with the following command:

    set openmode passive

Care should be taken with this option. You should also use this command to limit the amount of time that ppp(8) waits for the peer to begin negotiations:

    set stopped N

Alternatively, the following command (where `N` is the number of seconds to wait before starting negotiations) can be used:

    set openmode active N

Check the manual page for details.

13.13. Why does ppp(8) lock up when I shell out to test it?

When you execute the `shell` or `!` command, ppp(8) executes a shell (or if you have passed any arguments, ppp(8) will execute those arguments). The ppp program will wait for the command to complete before continuing. If you attempt to use the PPP link while running the command, the link will appear to have frozen. This is because ppp(8) is waiting for the command to complete.

To execute commands like this, use `!bg` instead. This will execute the given command in the background, and ppp(8) can continue to service the link.

13.14. Why does ppp(8) over a null-modem cable never exit?

There is no way for ppp(8) to automatically determine that a direct connection has been dropped. This is due to the lines that are used in a null-modem serial cable. When using this sort of connection, LQR should always be enabled with the following line:

    enable lqr

LQR is accepted by default if negotiated by the peer.

13.15. Why does ppp(8) dial for no reason in `-auto` mode?

If ppp(8) is dialing unexpectedly, you must determine the cause, and set up Dial filters (dfilters) to prevent such dialing.

To determine the cause, use the following line:

    set log +tcp/ip

This will log all traffic through the connection. The next time the line comes up unexpectedly, you will see the reason logged with a convenient timestamp next to it.

You can now disable dialing under these circumstances. Usually, this sort of problem arises due to DNS lookups. To prevent DNS lookups from establishing a connection (this will not prevent ppp(8) from passing the packets through an established connection), use the following:

    set dfilter 1 deny udp src eq 53
    set dfilter 2 deny udp dst eq 53
    set dfilter 3 permit 0/0 0/0

This is not always suitable, as it will effectively break your demand-dial capabilities — most programs will need a DNS lookup before doing any other network related things.

In the DNS case, you should try to determine what is actually trying to resolve a host name. A lot of the time, sendmail(8) is the culprit. You should make sure that you tell sendmail not to do any DNS lookups in its configuration file. See the section on using email with a dialup connection in the FreeBSD Handbook for details on how to create your own configuration file and what should go into it. You may also want to add the following line to `.mc`:

    define(`confDELIVERY_MODE', `d')dnl

This will make sendmail queue everything until the queue is run (usually, sendmail is run with `-bd -q30m`, telling it to run the queue every 30 minutes) or until a `sendmail `-q`` is done (perhaps from your `ppp.linkup`).

13.16. What do these CCP errors mean?

I keep seeing the following errors in my log file:

    CCP: CcpSendConfigReq
    CCP: Received Terminate Ack (1) state = Req-Sent (6)

This is because ppp(8) is trying to negotiate Predictor1 compression, and the peer does not want to negotiate any compression at all. The messages are harmless, but if you wish to remove them, you can disable Predictor1 compression locally too:

    disable pred1

13.17. Why does ppp(8) not log my connection speed?

To log all lines of your modem “conversation”, you must enable the following:

    set log +connect

This will make ppp(8) log everything up until the last requested “expect” string.

If you wish to see your connect speed and are using PAP or CHAP (and therefore do not have anything to “chat” after the CONNECT in the dial script — no `set login` script), you must make sure that you instruct ppp(8) to “expect” the whole CONNECT line, something like this:

    set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 4 \
      \"\" ATZ OK-ATZ-OK ATDT\\T TIMEOUT 60 CONNECT \\c \\n"

Here, we get our CONNECT, send nothing, then expect a line-feed, forcing ppp(8) to read the whole CONNECT response.

13.18. Why does ppp(8) ignore the `\` character in my chat script?

The ppp utility parses each line in your config files so that it can interpret strings such as `set phone "123 456 789"` correctly and realize that the number is actually only one argument. To specify a `"` character, you must escape it using a backslash (`\`).

When the chat interpreter parses each argument, it re-interprets the argument to find any special escape sequences such as `\P` or `\T` (see the manual page). As a result of this double-parsing, you must remember to use the correct number of escapes.

If you wish to actually send a `\` character to (say) your modem, you would need something like:

    set dial "\"\" ATZ OK-ATZ-OK AT\\\\X OK"

It will result in the following sequence:

    ATZ
    OK
    AT\X
    OK

Or:

    set phone 1234567
    set dial "\"\" ATZ OK ATDT\\T"

It will result in the following sequence:

    ATZ
    OK
    ATDT1234567

13.19. Why does ppp(8) get a “`Segmentation fault`”, but I see no `ppp.core`

The ppp utility (or any other program for that matter) should never dump core. Because ppp(8) runs setuid (with an effective user ID of `0`), the operating system will not write core image of ppp(8) to disk before terminating it. If, however ppp(8) is actually terminating due to a segmentation violation or some other signal that normally causes core to be dumped, and you are sure you are using the latest version (see the start of this section), then you should install the system sources and do the following:

    # cd /usr/src/usr.sbin/ppp
    # echo STRIP= >> /etc/make.conf
    # echo CFLAGS+=-g >> /etc/make.conf
    # make install clean

You will now have a debuggable version of ppp(8) installed. You will have to be `root` to run ppp(8) as all of its privileges have been revoked. When you start ppp(8), take a careful note of what your current directory was at the time.

Now, if and when ppp(8) receives the segmentation violation, it will dump a core file called `ppp.core`. You should then do the following:

    % su
    # gdb /usr/sbin/ppp ppp.core
    (gdb) bt
    .....
    (gdb) f 0
    ....
    (gdb) i args
    ....
    (gdb) l
    .....

All of this information should be given alongside your question, making it possible to diagnose the problem.

If you are familiar with gdb(1), you may wish to find out some other bits and pieces such as what actually caused the dump or the addresses and values of the relevant variables.

13.20. Why does the process that forces a dial in `-auto` mode never connect?

This was a known problem with ppp(8) set up to negotiate a dynamic local IP number with the peer in `-auto` mode. It has been fixed a long time ago — search the manual page for `iface`.

The problem was that when that initial program calls connect(2), the IP number of the tun(4) interface is assigned to the socket endpoint. The kernel creates the first outgoing packet and writes it to the tun(4) device. ppp(8) then reads the packet and establishes a connection. If, as a result of ppp(8)'s dynamic IP assignment, the interface address is changed, the original socket endpoint will be invalid. Any subsequent packets sent to the peer will usually be dropped. Even if they are not, any responses will not route back to the originating machine as the IP number is no longer owned by that machine.

There are several theoretical ways to approach this problem. It would be nicest if the peer would re-assign the same IP number if possible. The current version of ppp(8) does this, but most other implementations do not.

The easiest method from our side would be to never change the tun(4) interface IP number, but instead to change all outgoing packets so that the source IP number is changed from the interface IP to the negotiated IP on the fly. This is essentially what the `iface-alias` option in the latest version of ppp(8) is doing (with the help of libalias(3) and ppp(8)'s `-nat` switch) — it is maintaining all previous interface addresses and NATing them to the last negotiated address.

Another alternative (and probably the most reliable) would be to implement a system call that changes all bound sockets from one IP to another. ppp(8) would use this call to modify the sockets of all existing programs when a new IP number is negotiated. The same system call could be used by DHCP clients when they are forced to call the `bind()` function for their sockets.

Yet another possibility is to allow an interface to be brought up without an IP number. Outgoing packets would be given an IP number of `255.255.255.255` up until the first `SIOCAIFADDR` ioctl(2) is done. This would result in fully binding the socket. It would be up to ppp(8) to change the source IP number, but only if it is set to `255.255.255.255`, and only the IP number and IP checksum would need to change. This, however is a bit of a hack as the kernel would be sending bad packets to an improperly configured interface, on the assumption that some other mechanism is capable of fixing things retrospectively.

13.21. Why do most games not work with the `-nat` switch?

The reason games and the like do not work when libalias(3) is in use is that the machine on the outside will try to open a connection or send (unsolicited) UDP packets to the machine on the inside. The NAT software does not know that it should send these packets to the interior machine.

To make things work, make sure that the only thing running is the software that you are having problems with, then either run tcpdump(1) on the tun(4) interface of the gateway or enable ppp(8) TCP/IP logging (`set log +tcp/ip`) on the gateway.

When you start the offending software, you should see packets passing through the gateway machine. When something comes back from the outside, it will be dropped (that is the problem). Note the port number of these packets then shut down the offending software. Do this a few times to see if the port numbers are consistent. If they are, then the following line in the relevant section of `/etc/ppp/ppp.conf` will make the software functional:

    nat port proto internalmachine:port port

where `proto` is either `tcp` or `udp`, `internalmachine` is the machine that you want the packets to be sent to and `port` is the destination port number of the packets.

You will not be able to use the software on other machines without changing the above command, and running the software on two internal machines at the same time is out of the question — after all, the outside world is seeing your entire internal network as being just a single machine.

If the port numbers are not consistent, there are three more options:

1. Submit support in libalias(3). Examples of “special cases” can be found in `/usr/src/sys/netinet/libalias/alias_*.c` (`alias_ftp.c` is a good prototype). This usually involves reading certain recognized outgoing packets, identifying the instruction that tells the outside machine to initiate a connection back to the internal machine on a specific (random) port and setting up a “route” in the alias table so that the subsequent packets know where to go.

   This is the most difficult solution, but it is the best and will make the software work with multiple machines.

2. Use a proxy. The application may support `socks5` for example, or may have a “passive” option that avoids ever requesting that the peer open connections back to the local machine.

3. Redirect everything to the internal machine using `nat addr`. This is the sledge-hammer approach.

13.22. What are FCS errors?

FCS stands for Frame Check Sequence. Each PPP packet has a checksum attached to ensure that the data being received is the data being sent. If the FCS of an incoming packet is incorrect, the packet is dropped and the HDLC FCS count is increased. The HDLC error values can be displayed using the `show hdlc` command.

If your link is bad (or if your serial driver is dropping packets), you will see the occasional FCS error. This is not usually worth worrying about although it does slow down the compression protocols substantially. If you have an external modem, make sure your cable is properly shielded from interference — this may eradicate the problem.

If your link freezes as soon as you have connected and you see a large number of FCS errors, this may be because your link is not 8-bit clean. Make sure your modem is not using software flow control (XON/XOFF). If your datalink must use software flow control, use the command `set accmap 0x000a0000` to tell ppp(8) to escape the `^Q` and `^S` characters.

Another reason for seeing too many FCS errors may be that the remote end has stopped talking PPP. You may want to enable `async` logging at this point to determine if the incoming data is actually a login or shell prompt. If you have a shell prompt at the remote end, it is possible to terminate ppp(8) without dropping the line by using `close lcp` (a following `term`) will reconnect you to the shell on the remote machine.

If nothing in your log file indicates why the link might have been terminated, you should ask the remote administrator (your ISP?) why the session was terminated.

13.23. None of this helps — I am desperate! What can I do?

If all else fails, send as much information as you can, including your config files, how you are starting ppp(8), the relevant parts of your log file and the output of `netstat -rn` (before and after connecting) to the FreeBSD general questions mailing list and someone should point you in the right direction.

# Chapter 14 Serial Communications

This section answers common questions about serial communications with FreeBSD. PPP is covered in the Networking section.

14.1. Which multi-port serial cards are supported by FreeBSD?
14.2. How do I get the boot: prompt to show on the serial console?
14.3. How do I tell if FreeBSD found my serial ports or modem cards?
14.4. How do I access the serial ports on FreeBSD?
14.5. How do I enable support for a multiport serial card?
14.6. Can I set the default serial parameters for a port?
14.7. How can I enable dialup logins on my modem?
14.8. How can I connect a dumb terminal to my FreeBSD box?
14.9. Why can I not run `tip` or `cu`?

14.1. Which multi-port serial cards are supported by FreeBSD?

There is a list of these in the Serial Communications chapter of the handbook.

Most multi-port PCI cards that are based on 16550 or clones are supported with no extra effort.

Some unnamed clone cards have also been known to work, especially those that claim to be AST compatible.

Check uart(4) and sio(4) to get more information on configuring such cards.

14.2. How do I get the boot: prompt to show on the serial console?

See this section of the handbook.

14.3. How do I tell if FreeBSD found my serial ports or modem cards?

As the FreeBSD kernel boots, it will probe for the serial ports in your system for which the kernel was configured. You can either watch your system closely for the messages it prints or run this command after your system is up and running:

    % dmesg | grep -E "^sio[0-9]"

Here is some example output from the above command:

    sio0: <16550A-compatible COM port> port 0x3f8-0x3ff irq 4 flags 0x10 on acpi0
    sio0: type 16550A
    sio1: <16550A-compatible COM port> port 0x2f8-0x2ff irq 3 on acpi0
    sio1: type 16550A

This shows two serial ports. The first is on IRQ 4, is using port address `0x3f8`, and has a 16550A-type UART chip. The second uses the same kind of chip but is on IRQ 3 and is at port address `0x2f8`. Internal modem cards are treated just like serial ports — except that they always have a modem “attached” to the port.

The `GENERIC` kernel includes support for two serial ports using the same IRQ and port address settings in the above example. If these settings are not right for your system, or if you have added modem cards or have more serial ports than your kernel is configured for, just reconfigure your kernel. See section about building a kernel for more details.

14.4. How do I access the serial ports on FreeBSD?

The third serial port, `sio2` (see sio(4), known as `COM3` in DOS), is on `/dev/cuad2` for dial-out devices, and on `/dev/ttyd2` for dial-in devices. What is the difference between these two classes of devices?

You use `ttyd`X`` for dial-ins. When opening `/dev/ttyd`X`` in blocking mode, a process will wait for the corresponding `cuad`X`` device to become inactive, and then wait for the carrier detect line to go active. When you open the `cuad`X`` device, it makes sure the serial port is not already in use by the `ttyd`X`` device. If the port is available, it “steals” it from the `ttyd`X`` device. Also, the `cuad`X`` device does not care about carrier detect. With this scheme and an auto-answer modem, you can have remote users log in and you can still dial out with the same modem and the system will take care of all the conflicts.

14.5. How do I enable support for a multiport serial card?

Again, the section on kernel configuration provides information about configuring your kernel. For a multiport serial card, place an sio(4) line for each serial port on the card in the device.hints(5) file. But place the IRQ specifiers on only one of the entries. All of the ports on the card should share one IRQ. For consistency, use the last serial port to specify the IRQ. Also, specify the following option in the kernel configuration file:

    options COM_MULTIPORT

The following `/boot/device.hints` example is for an AST 4-port serial card on IRQ 12:

    hint.sio.4.at="isa"
    hint.sio.4.port="0x2a0"
    hint.sio.4.flags="0x701"
    hint.sio.5.at="isa"
    hint.sio.5.port="0x2a8"
    hint.sio.5.flags="0x701"
    hint.sio.6.at="isa"
    hint.sio.6.port="0x2b0"
    hint.sio.6.flags="0x701"
    hint.sio.7.at="isa"
    hint.sio.7.port="0x2b8"
    hint.sio.7.flags="0x701"
    hint.sio.7.irq="12"

The flags indicate that the master port has minor number `7` (`0x700`), and all the ports share an IRQ (`0x001`).

14.6. Can I set the default serial parameters for a port?

See the Serial Communications section in the FreeBSD Handbook.

14.7. How can I enable dialup logins on my modem?

Please read the section about Dial-in Services in the FreeBSD Handbook.

14.8. How can I connect a dumb terminal to my FreeBSD box?

You can find this information in the Terminals section of the FreeBSD Handbook.

14.9. Why can I not run `tip` or `cu`?

On your system, the programs tip(1) and cu(1) can only access the `/var/spool/lock` directory via user `uucp` and group `dialer`. You can use the group `dialer` to control who has access to your modem or remote systems. Just add yourself to group `dialer`.

Alternatively, you can let everyone on your system run tip(1) and cu(1) by typing:

    # chmod 4511 /usr/bin/cu
    # chmod 4511 /usr/bin/tip

# Chapter 15 Miscellaneous Questions

15.1. FreeBSD a lot of swap space even when the computer has free memory left. Why?
15.2. Why does `top` show very little free memory even when I have very few programs running?
15.3. Why will `chmod` not change the permissions on symlinks?
15.4. Can I run DOS binaries under FreeBSD?
15.5. What do I need to do to translate a FreeBSD document into my native language?
15.6. Why does my email to any address at `FreeBSD.org` bounce?
15.7. Where can I find a free FreeBSD account?
15.8. What is the cute little red guy's name?
15.9. Can I use the BSD daemon image?
15.10. Do you have any BSD daemon images I could use?
15.11. I have seen an acronym or other term on the mailing lists and I do not understand what it means. Where should I look?
15.12. Why should I care what color the bikeshed is?

15.1. FreeBSD a lot of swap space even when the computer has free memory left. Why?

FreeBSD will proactively move entirely idle, unused pages of main memory into swap in order to make more main memory available for active use. This heavy use of swap is balanced by using the extra free memory for cacheing.

Note that while FreeBSD is proactive in this regard, it does not arbitrarily decide to swap pages when the system is truly idle. Thus you will not find your system all paged out when you get up in the morning after leaving it idle overnight.

15.2. Why does `top` show very little free memory even when I have very few programs running?

The simple answer is that free memory is wasted memory. Any memory that your programs do not actively allocate is used within the FreeBSD kernel as disk cache. The values shown by top(1) labeled as `Inact`, `Cache`, and `Buf` are all cached data at different aging levels. This cached data means the system does not have to access a slow disk again for data it has accessed recently, thus increasing overall performance. In general, a low value shown for `Free` memory in top(1) is good, provided it is not very low.

15.3. Why will `chmod` not change the permissions on symlinks?

Symlinks do not have permissions, and by default, chmod(1) will follow symlinks to change the permissions on the source file, if possible. So if you have a file, `foo`, and a symlink to that file, `bar`, then this command will always succeed.

    % chmod g-w bar

However, the permissions on `bar` will not have changed.

When changing modes of the file hierarchies rooted in the files instead of the files themselves, you have to use either `-H` or `-L` together with `-R` to make this work. See chmod(1) and symlink(7) for more information.

> Warning: `-R` does a recursive chmod(1). Be careful about specifying directories or symlinks to directories to chmod(1). If you want to change the permissions of a directory referenced by a symlink, use chmod(1) without any options and follow the symlink with a trailing slash (`/`). For example, if `foo` is a symlink to directory `bar`, and you want to change the permissions of `foo` (actually `bar`), you would do something like:

>     % chmod 555 foo/

> With the trailing slash, chmod(1) will follow the symlink, `foo`, to change the permissions of the directory, `bar`.

15.4. Can I run DOS binaries under FreeBSD?

Yes, you can use `emulators/doscmd`, a DOS emulation program, available in the FreeBSD Ports Collection.

If doscmd will not suffice, the add-on utility `emulators/pcemu` emulates an 8088 and enough BIOS services to run many DOS text mode applications. It requires the X Window System.

You may also try `emulators/dosbox` from the FreeBSD Ports Collection. The main focus of this application is emulating old DOS games using the local file system for files.

15.5. What do I need to do to translate a FreeBSD document into my native language?

See the Translation FAQ in the FreeBSD Documentation Project Primer.

15.6. Why does my email to any address at `FreeBSD.org` bounce?

The `FreeBSD.org` mail system implements some Postfix checks on incoming mail and rejects mail that is either from misconfigured relays or otherwise appears likely to be spam. Some of the specific requirements are:

- The IP address of the SMTP client must "reverse-resolve" to a forward confirmed hostname.

- The fully-qualified hostname given in the SMTP conversation (either HELO or EHLO) must resolve to the IP address of the client.

Other advice to help your mail reach its destination include:

- Mail should be sent in plain text, and messages sent to mailing lists should generally be no more than 200KB in length.

- Avoid excessive cross posting. Choose one mailing list which seems most relevant and send it there.

If you still have trouble with email infrastructure at `FreeBSD.org` send a note with the details to `<postmaster@freebsd.org>`; Include a date/time interval so that logs may be reviewed — and note that we only keep one week's worth of mail logs. (Be sure to specify the time zone or offset from UTC.)

15.7. Where can I find a free FreeBSD account?

While FreeBSD does not provide open access to any of their servers, others do provide open access UNIX systems. The charge varies and limited services may be available.

Arbornet, Inc, also known as M-Net, has been providing open access to UNIX systems since 1983. Starting on an Altos running System III, the site switched to BSD/OS in 1991. In June of 2000, the site switched again to FreeBSD. M-Net can be accessed via telnet and SSH and provides basic access to the entire FreeBSD software suite. However, network access is limited to members and patrons who donate to the system, which is run as a non-profit organization. M-Net also provides an bulletin board system and interactive chat.

15.8. What is the cute little red guy's name?

He does not have one, and is just called “the BSD daemon”. If you insist upon using a name, call him “beastie”. Note that “beastie” is pronounced “BSD”.

You can learn more about the BSD daemon on his home page.

15.9. Can I use the BSD daemon image?

Perhaps. The BSD daemon is copyrighted by Marshall Kirk McKusick. You will want to check his Statement on the Use of the BSD Daemon Figure for detailed usage terms.

In summary, you are free to use the image in a tasteful manner, for personal use, so long as appropriate credit is given. If you want to use him commercially, you must contact Kirk McKusick `<mckusick@FreeBSD.org>`. More details are available on the BSD Daemon's home page.

15.10. Do you have any BSD daemon images I could use?

You will find eps and Xfig drawings under `/usr/share/examples/BSD_daemon/`.

15.11. I have seen an acronym or other term on the mailing lists and I do not understand what it means. Where should I look?

Please see the FreeBSD Glossary.

15.12. Why should I care what color the bikeshed is?

The really, really short answer is that you should not. The somewhat longer answer is that just because you are capable of building a bikeshed does not mean you should stop others from building one just because you do not like the color they plan to paint it. This is a metaphor indicating that you need not argue about every little feature just because you know enough to do so. Some people have commented that the amount of noise generated by a change is inversely proportional to the complexity of the change.

The longer and more complete answer is that after a very long argument about whether sleep(1) should take fractional second arguments, Poul-Henning Kamp `<phk@FreeBSD.org>` posted a long message entitled “A bike shed (any color will do) on greener grass...”. The appropriate portions of that message are quoted below.

“What is it about this bike shed?” Some of you have asked me.

It is a long story, or rather it is an old story, but it is quite short actually. C. Northcote Parkinson wrote a book in the early 1960s, called “Parkinson's Law”, which contains a lot of insight into the dynamics of management.

[snip a bit of commentary on the book]

In the specific example involving the bike shed, the other vital component is an atomic power-plant, I guess that illustrates the age of the book.

Parkinson shows how you can go into the board of directors and get approval for building a multi-million or even billion dollar atomic power plant, but if you want to build a bike shed you will be tangled up in endless discussions.

Parkinson explains that this is because an atomic plant is so vast, so expensive and so complicated that people cannot grasp it, and rather than try, they fall back on the assumption that somebody else checked all the details before it got this far. Richard P. Feynmann gives a couple of interesting, and very much to the point, examples relating to Los Alamos in his books.

A bike shed on the other hand. Anyone can build one of those over a weekend, and still have time to watch the game on TV. So no matter how well prepared, no matter how reasonable you are with your proposal, somebody will seize the chance to show that he is doing his job, that he is paying attention, that he is here.

In Denmark we call it “setting your fingerprint”. It is about personal pride and prestige, it is about being able to point somewhere and say “There! I did that.” It is a strong trait in politicians, but present in most people given the chance. Just think about footsteps in wet cement.

--Poul-Henning Kamp `<phk@FreeBSD.org>` on freebsd-hackers, October 2, 1999 |

# Chapter 16 The FreeBSD Funnies

16.1. How cool is FreeBSD?
16.2. Who is scratching in my memory banks??
16.3. How many FreeBSD hackers does it take to change a lightbulb?
16.4. Where does data written to `/dev/null` go?
16.5. My colleague sits at the computer too much, how can I prank her?

16.1. How cool is FreeBSD?

Q. Has anyone done any temperature testing while running FreeBSD? I know Linux runs cooler than DOS, but have never seen a mention of FreeBSD. It seems to run really hot.

A. No, but we have done numerous taste tests on blindfolded volunteers who have also had 250 micrograms of LSD-25 administered beforehand. 35% of the volunteers said that FreeBSD tasted sort of orange, whereas Linux tasted like purple haze. Neither group mentioned any significant variances in temperature. We eventually had to throw the results of this survey out entirely anyway when we found that too many volunteers were wandering out of the room during the tests, thus skewing the results. We think most of the volunteers are at Apple now, working on their new “scratch and sniff” GUI. It is a funny old business we are in!

Seriously, FreeBSD uses the HLT (halt) instruction when the system is idle thus lowering its energy consumption and therefore the heat it generates. Also if you have ACPI (Advanced Configuration and Power Interface) configured, then FreeBSD can also put the CPU into a low power mode.

16.2. Who is scratching in my memory banks??

Q. Is there anything “odd” that FreeBSD does when compiling the kernel which would cause the memory to make a scratchy sound? When compiling (and for a brief moment after recognizing the floppy drive upon startup, as well), a strange scratchy sound emanates from what appears to be the memory banks.

A. Yes! You will see frequent references to “daemons” in the BSD documentation, and what most people do not know is that this refers to genuine, non-corporeal entities that now possess your computer. The scratchy sound coming from your memory is actually high-pitched whispering exchanged among the daemons as they best decide how to deal with various system administration tasks.

If the noise gets to you, a good `fdisk /mbr` from DOS will get rid of them, but do not be surprised if they react adversely and try to stop you. In fact, if at any point during the exercise you hear the satanic voice of Bill Gates coming from the built-in speaker, take off running and do not ever look back! Freed from the counterbalancing influence of the BSD daemons, the twin demons of DOS and Windows are often able to re-assert total control over your machine to the eternal damnation of your soul. Now that you know, given a choice you would probably prefer to get used to the scratchy noises, no?

16.3. How many FreeBSD hackers does it take to change a lightbulb?

One thousand, one hundred and sixty-nine:

Twenty-three to complain to -CURRENT about the lights being out;

Four to claim that it is a configuration problem, and that such matters really belong on -questions;

Three to submit PRs about it, one of which is misfiled under doc and consists only of “it's dark”;

One to commit an untested lightbulb which breaks buildworld, then back it out five minutes later;

Eight to flame the PR originators for not including patches in their PRs;

Five to complain about buildworld being broken;

Thirty-one to answer that it works for them, and they must have updated at a bad time;

One to post a patch for a new lightbulb to -hackers;

One to complain that he had patches for this three years ago, but when he sent them to -CURRENT they were just ignored, and he has had bad experiences with the PR system; besides, the proposed new lightbulb is non-reflexive;

Thirty-seven to scream that lightbulbs do not belong in the base system, that committers have no right to do things like this without consulting the Community, and WHAT IS -CORE DOING ABOUT IT!?

Two hundred to complain about the color of the bicycle shed;

Three to point out that the patch breaks style(9);

Seventeen to complain that the proposed new lightbulb is under GPL;

Five hundred and eighty-six to engage in a flame war about the comparative advantages of the GPL, the BSD license, the MIT license, the NPL, and the personal hygiene of unnamed FSF founders;

Seven to move various portions of the thread to -chat and -advocacy;

One to commit the suggested lightbulb, even though it shines dimmer than the old one;

Two to back it out with a furious flame of a commit message, arguing that FreeBSD is better off in the dark than with a dim lightbulb;

Forty-six to argue vociferously about the backing out of the dim lightbulb and demanding a statement from -core;

Eleven to request a smaller lightbulb so it will fit their Tamagotchi if we ever decide to port FreeBSD to that platform;

Seventy-three to complain about the SNR on -hackers and -chat and unsubscribe in protest;

Thirteen to post “unsubscribe”, “How do I unsubscribe?”, or “Please remove me from the list”, followed by the usual footer;

One to commit a working lightbulb while everybody is too busy flaming everybody else to notice;

Thirty-one to point out that the new lightbulb would shine 0.364% brighter if compiled with TenDRA (although it will have to be reshaped into a cube), and that FreeBSD should therefore switch to TenDRA instead of GCC;

One to complain that the new lightbulb lacks fairings;

Nine (including the PR originators) to ask “what is MFC?”;

Fifty-seven to complain about the lights being out two weeks after the bulb has been changed.

Nik Clayton `<nik@FreeBSD.org>` adds:

I was laughing quite hard at this.

And then I thought, “Hang on, shouldn't there be '1 to document it.' in that list somewhere?”

And then I was enlightened :-)

Thomas Abthorpe `<tabthorpe@FreeBSD.org>` says: “None, real FreeBSD hackers are not afraid of the dark!”

16.4. Where does data written to `/dev/null` go?

It goes into a special data sink in the CPU where it is converted to heat which is vented through the heatsink / fan assembly. This is why CPU cooling is increasingly important; as people get used to faster processors, they become careless with their data and more and more of it ends up in `/dev/null`, overheating their CPUs. If you delete `/dev/null` (which effectively disables the CPU data sink) your CPU may run cooler but your system will quickly become constipated with all that excess data and start to behave erratically. If you have a fast network connection you can cool down your CPU by reading data out of `/dev/random` and sending it off somewhere; however you run the risk of overheating your network connection and `/` or angering your ISP, as most of the data will end up getting converted to heat by their equipment, but they generally have good cooling, so if you do not overdo it you should be OK.

Paul Robinson adds:

There are other methods. As every good sysadmin knows, it is part of standard practice to send data to the screen of interesting variety to keep all the pixies that make up your picture happy. Screen pixies (commonly mis-typed or re-named as “pixels”) are categorized by the type of hat they wear (red, green or blue) and will hide or appear (thereby showing the color of their hat) whenever they receive a little piece of food. Video cards turn data into pixie-food, and then send them to the pixies — the more expensive the card, the better the food, so the better behaved the pixies are. They also need constant stimulation — this is why screen savers exist.

To take your suggestions further, you could just throw the random data to console, thereby letting the pixies consume it. This causes no heat to be produced at all, keeps the pixies happy and gets rid of your data quite quickly, even if it does make things look a bit messy on your screen.

Incidentally, as an ex-admin of a large ISP who experienced many problems attempting to maintain a stable temperature in a server room, I would strongly discourage people sending the data they do not want out to the network. The fairies who do the packet switching and routing get annoyed by it as well.

16.5. My colleague sits at the computer too much, how can I prank her?

Install `games/sl` and wait for her to mistype `sl` for `ls`.

# Chapter 17 Advanced Topics

17.1. How can I learn more about FreeBSD's internals?
17.2. How can I contribute to FreeBSD?
17.3. What are snapshots and releases?
17.4. Can I follow -CURRENT with limited Internet access?
17.5. I have written a kernel extension, who do I send it to?
17.6. How can I make the most of the data I see when my kernel panics?
17.7. Why has `dlsym()` stopped working for ELF executables?
17.8. How can I increase or reduce the kernel address space on i386?

17.1. How can I learn more about FreeBSD's internals?

See the FreeBSD Architecture Handbook.

Additionally, much general UNIX knowledge is directly applicable to FreeBSD.

17.2. How can I contribute to FreeBSD?

Please see the article on Contributing to FreeBSD for specific advice on how to do this. Assistance is more than welcome!

17.3. What are snapshots and releases?

There are currently four active/semi-active branches in the FreeBSD Subversion Repository. (Earlier branches are only changed very rarely, which is why there are only four active branches of development):

- `RELENG_8` AKA 8-STABLE

- `RELENG_9` AKA 9-STABLE

- `HEAD` AKA -CURRENT AKA 10-CURRENT

`HEAD` is not an actual branch tag, like the others; it is simply a symbolic constant for “the current, non-branched development stream” which we simply refer to as -CURRENT.

Right now, -CURRENT is the 10.`X` development stream; the 9-STABLE branch, `RELENG_9`, forked off from -CURRENT in September 2011 and the 8-STABLE branch, `RELENG_8`, forked off from -CURRENT in August 2009.

17.4. Can I follow -CURRENT with limited Internet access?

Yes, you can do this without downloading the whole source tree by using the CTM facility.

17.5. I have written a kernel extension, who do I send it to?

Please take a look at the article on Contributing to FreeBSD to learn how to submit code.

And thanks for the thought!

17.6. How can I make the most of the data I see when my kernel panics?

Here is typical kernel panic:

    Fatal trap 12: page fault while in kernel mode
    fault virtual address   = 0x40
    fault code              = supervisor read, page not present
    instruction pointer     = 0x8:0xf014a7e5
    stack pointer           = 0x10:0xf4ed6f24
    frame pointer           = 0x10:0xf4ed6f28
    code segment            = base 0x0, limit 0xfffff, type 0x1b
                            = DPL 0, pres 1, def32 1, gran 1
    processor eflags        = interrupt enabled, resume, IOPL = 0
    current process         = 80 (mount)
    interrupt mask          =
    trap number             = 12
    panic: page fault

When you see a message like this, it is not enough to just reproduce it and send it in. The instruction pointer value is important; unfortunately, it is also configuration dependent. In other words, the value varies depending on the exact kernel image that you are using. If you are using a `GENERIC` kernel image from one of the snapshots, then it is possible for somebody else to track down the offending function, but if you are running a custom kernel then only you can tell us where the fault occurred.

What you should do is this:

1. Write down the instruction pointer value. Note that the `0x8:` part at the beginning is not significant in this case: it is the `0xf0xxxxxx` part that we want.

2. When the system reboots, do the following:

       % nm -n kernel.that.caused.the.panic | grep f0xxxxxx

   where `f0xxxxxx` is the instruction pointer value. The odds are you will not get an exact match since the symbols in the kernel symbol table are for the entry points of functions and the instruction pointer address will be somewhere inside a function, not at the start. If you do not get an exact match, omit the last digit from the instruction pointer value and try again, i.e.:

       % nm -n kernel.that.caused.the.panic | grep f0xxxxx

   If that does not yield any results, chop off another digit. Repeat until you get some sort of output. The result will be a possible list of functions which caused the panic. This is a less than exact mechanism for tracking down the point of failure, but it is better than nothing.

However, the best way to track down the cause of a panic is by capturing a crash dump, then using kgdb(1) to generate a stack trace on the crash dump.

In any case, the method is this:

1. Make sure that the following line is included in your kernel configuration file (`/usr/src/sys/`arch`/conf/`MYKERNEL``):

       makeoptions     DEBUG=-g          # Build kernel with gdb(1) debug symbols

2. Change to the `/usr/src` directory:

       # cd /usr/src

3. Compile the kernel:

       # make buildkernel KERNCONF=MYKERNEL

4. Wait for make(1) to finish compiling.

5.     # make installkernel KERNCONF=MYKERNEL

6. Reboot.

> Note: If you do not use the `KERNCONF` make variable a `GENERIC` kernel will be built and installed.

The make(1) process will have built two kernels. `/usr/obj/usr/src/sys/`MYKERNEL`/kernel` and `/usr/obj/usr/src/sys/`MYKERNEL`/kernel.debug`. `kernel` was installed as `/boot/kernel/kernel`, while `kernel.debug` can be used as the source of debugging symbols for kgdb(1).

To make sure you capture a crash dump, you need edit `/etc/rc.conf` and set `dumpdev` to point to your swap partition (or `AUTO`). This will cause the rc(8) scripts to use the dumpon(8) command to enable crash dumps. You can also run dumpon(8) manually. After a panic, the crash dump can be recovered using savecore(8); if `dumpdev` is set in `/etc/rc.conf`, the rc(8) scripts will run savecore(8) automatically and put the crash dump in `/var/crash`.

> Note: FreeBSD crash dumps are usually the same size as the physical RAM size of your machine. That is, if you have 512 MB of RAM, you will get a 512 MB crash dump. Therefore you must make sure there is enough space in `/var/crash` to hold the dump. Alternatively, you run savecore(8) manually and have it recover the crash dump to another directory where you have more room. It is possible to limit the size of the crash dump by using `options MAXMEM=`N`` where `N` is the size of kernel's memory usage in KBs. For example, if you have 1 GB of RAM, you can limit the kernel's memory usage to 128 MB by this way, so that your crash dump size will be 128 MB instead of 1 GB.

Once you have recovered the crash dump, you can get a stack trace with kgdb(1) as follows:

    % kgdb /usr/obj/usr/src/sys/MYKERNEL/kernel.debug /var/crash/vmcore.0
    (kgdb) backtrace

Note that there may be several screens worth of information; ideally you should use script(1) to capture all of them. Using the unstripped kernel image with all the debug symbols should show the exact line of kernel source code where the panic occurred. Usually you have to read the stack trace from the bottom up to trace the exact sequence of events that lead to the crash. You can also use kgdb(1) to print out the contents of various variables or structures to examine the system state at the time of the crash.

> Tip: Now, if you are really insane and have a second computer, you can also configure kgdb(1) to do remote debugging such that you can use kgdb(1) on one system to debug the kernel on another system, including setting breakpoints, single-stepping through the kernel code, just like you can do with a normal user-mode program.

> Note: If you have `DDB` enabled and the kernel drops into the debugger, you can force a panic (and a crash dump) just by typing `panic` at the `ddb` prompt. It may stop in the debugger again during the panic phase. If it does, type `continue` and it will finish the crash dump.

17.7. Why has `dlsym()` stopped working for ELF executables?

The ELF toolchain does not, by default, make the symbols defined in an executable visible to the dynamic linker. Consequently `dlsym()` searches on handles obtained from calls to `dlopen(NULL, flags)` will fail to find such symbols.

If you want to search, using `dlsym()`, for symbols present in the main executable of a process, you need to link the executable using the `--export-dynamic` option to the ELF linker (ld(1)).

17.8. How can I increase or reduce the kernel address space on i386?

By default, the kernel address space is 1 GB (2 GB for PAE) for i386. If you run a network-intensive server (e.g., a FTP or HTTP server), or you want to use ZFS, you might find that is not enough.

Add the following line to your kernel configuration file to increase available space and rebuild your kernel:

    options KVA_PAGES=N

To find the correct value of `N`, divide the desired address space size (in megabytes) by four. (For example, it is `512` for 2 GB.)

# Chapter 18 Acknowledgments

This innocent little Frequently Asked Questions document has been written, rewritten, edited, folded, spindled, mutilated, eviscerated, contemplated, discombobulated, cogitated, regurgitated, rebuilt, castigated, and reinvigorated over the last decade, by a cast of hundreds if not thousands. Repeatedly.

We wish to thank every one of the people responsible, and we encourage you to join them in making this FAQ even better.

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Pentium Processor System Architecture, Don Anderson and Tom Shanley, Addison-Wesley, 1995, 2nd edition, ISBN 0-201-40992-5.

Programmer's Guide to the EGA, VGA, and Super VGA Cards, Richard F. Ferraro, 3rd edition, Addison-Wesley, 1995, ISBN 0-201-62490-7.

80486 System Architecture, Tom Shanley, Addison-Wesley, 1995, 3rd edition, ISBN 0-201-40994-1.

ISA System Architecture, Tom Shanley, Addison-Wesley, 3rd edition, 1995, ISBN 0-201-40996-8.

PCI System Architecture, Tom Shanley, Addison-Wesley, 1995, 3rd edition, ISBN 0-201-40993-3.

The Undocumented PC, Frank Van Gilluwe, Addison-Wesley, 1994, ISBN 0-201-62277-7.

Bell System Technical Journal, Unix Time-Sharing System, American Telephone & Telegraph Company, July-August 1978, Vol 57, No 6, Part 2, ISSN0005-8580.

Lion's Commentary on UNIX, John Lion, ITP Media Group, 1996, 6th edition, ISBN 1573980137.

The New Hacker's Dictionary, Eric S. Raymond, MIT Press, 1996, 3rd edition, ISBN 0-262-68092-0.

A quarter century of UNIX, Peter H. Salus, Addison-Wesley, 1994, ISBN 0-201-54777-5.

The UNIX-HATERS Handbook, Steven Strassman, Daniel Weise, and Simon Garfinkel, IDG Books Worldwide, Inc, 1994, ISBN 1-56884-203-1.

Life with UNIX — special edition, Don Libes and Sandy Ressler, Prentice-Hall, 1989, ISBN 0-13-536657-7.

The BSD Family Tree, 1997.

Absolute BSD, Michael Lucas, No Starch Press, June 2002, ISBN 1-886411-74-3.

The C/C++ Users Journal, R&D Publications Inc., ISSN 1075-2838.

Sys Admin — The Journal for UNIX System Administrators, Miller Freeman, Inc, ISSN 1061-2688.