       Installing and Using FreeBSD With Other Operating Systems

  Jay Richmond

       <jayrich@sysc.com>
     

   6 August 1996

   FreeBSD is a registered trademark of the FreeBSD Foundation.

   IBM, AIX, EtherJet, Netfinity, OS/2, PowerPC, PS/2, S/390, and
   ThinkPad are trademarks of International Business Machines
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   Microsoft, IntelliMouse, MS-DOS, Outlook, Windows, Windows Media
   and Windows NT are either registered trademarks or trademarks of
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   PowerQuest and PartitionMagic are registered trademarks of
   PowerQuest Corporation in the United States and/or other
   countries.

   Many of the designations used by manufacturers and sellers to
   distinguish their products are claimed as trademarks. Where those
   designations appear in this document, and the FreeBSD Project was
   aware of the trademark claim, the designations have been followed
   by the "(TM)" or the "(R)" symbol.

   This document discusses how to make FreeBSD coexist nicely with
   other popular operating systems such as Linux, MS-DOS(R), OS/2(R),
   and Windows(R) 95. Special thanks to: Annelise Anderson
   <andrsn@stanford.edu>, Randall Hopper <rhh@ct.picker.com>, and
   Jordan K. Hubbard <jkh@FreeBSD.org>.

     --------------------------------------------------------------

1 Overview

   Most people can not fit these operating systems together
   comfortably without having a larger hard disk, so special
   information on large EIDE drives is included. Because there are so
   many combinations of possible operating systems and hard disk
   configurations, the Section 5 section may be of the most use to
   you. It contains descriptions of specific working computer setups
   that use multiple operating systems.

   This document assumes that you have already made room on your hard
   disk for an additional operating system. Any time you repartition
   your hard drive, you run the risk of destroying the data on the
   original partitions. However, if your hard drive is completely
   occupied by DOS, you might find the FIPS utility (included on the
   FreeBSD CDROM in the \TOOLS directory or via ftp) useful. It lets
   you repartition your hard disk without destroying the data already
   on it. There is also a commercial program available called
   PartitionMagic(R), which lets you size and delete partitions
   without consequence.

     --------------------------------------------------------------

2 Overview of Boot Managers

   These are just brief descriptions of some of the different boot
   managers you may encounter. Depending on your computer setup, you
   may find it useful to use more than one of them on the same
   system.

   Boot Easy

           This is the default boot manager used with FreeBSD. It has
           the ability to boot most anything, including BSD, OS/2
           (HPFS), Windows 95 (FAT and FAT32), and Linux. Partitions
           are selected with the function keys.

   OS/2 Boot Manager

           This will boot FAT, FAT32, HPFS, FFS (FreeBSD), and EXT2
           (Linux). Partitions are selected using arrow keys. The
           OS/2 Boot Manager is the only one to use its own separate
           partition, unlike the others which use the master boot
           record (MBR). Therefore, it must be installed below the
           1024th cylinder to avoid booting problems. It can boot
           Linux using LILO when it is part of the boot sector, not
           the MBR. Go to Linux HOWTOs on the World Wide Web for more
           information on booting Linux with the OS/2 boot manager.

   OS-BS

           This is an alternative to Boot Easy. It gives you more
           control over the booting process, with the ability to set
           the default partition to boot and the booting timeout. The
           beta version of this programs allows you to boot by
           selecting the OS with your arrow keys. It is included on
           the FreeBSD CD in the \TOOLS directory, and via ftp.

   LILO, or LInux LOader

           This is a limited boot manager. It will boot FreeBSD,
           though some customization work is required in the LILO
           configuration file.

     About FAT32: FAT32 is the replacement to the FAT filesystem
     included in Microsoft's OEM SR2 Beta release, which started
     replacing FAT on computers pre-loaded with Windows 95 towards
     the end of 1996. It converts the normal FAT filesystem and
     allows you to use smaller cluster sizes for larger hard drives.
     FAT32 also modifies the traditional FAT boot sector and
     allocation table, making it incompatible with some boot
     managers.

     --------------------------------------------------------------

3 A Typical Installation

   Let's say I have two large EIDE hard drives, and I want to install
   FreeBSD, Linux, and Windows 95 on them.

   Here is how I might do it using these hard disks:

     * /dev/wd0 (first physical hard disk)

     * /dev/wd1 (second hard disk)

   Both disks have 1416 cylinders.

    1. I boot from a MS-DOS or Windows 95 boot disk that contains the
       FDISK.EXE utility and make a small 50 MB primary partition
       (35-40 for Windows 95, plus a little breathing room) on the
       first disk. Also create a larger partition on the second hard
       disk for my Windows applications and data.

    2. I reboot and install Windows 95 (easier said than done) on the
       C: partition.

    3. The next thing I do is install Linux. I am not sure about all
       the distributions of Linux, but Slackware includes LILO (see
       Section 2). When I am partitioning out my hard disk with Linux
       fdisk, I would put all of Linux on the first drive (maybe
       300 MB for a nice root partition and some swap space).

    4. After I install Linux, and are prompted about installing LILO,
       make sure that I install it on the boot sector of my root
       Linux partition, not in the MBR (master boot record).

    5. The remaining hard disk space can go to FreeBSD. I also make
       sure that my FreeBSD root slice does not go beyond the 1024th
       cylinder. (The 1024th cylinder is 528 MB into the disk with
       our hypothetical 720 MB disks). I will use the rest of the
       hard drive (about 270 MB) for the /usr and / slices if I wish.
       The rest of the second hard disk (size depends on the amount
       of my Windows application/data partition that I created in
       step 1) can go to the /usr/src slice and swap space.

    6. When viewed with the Windows 95 fdisk utility, my hard drives
       should now look something like this:

 ---------------------------------------------------------------------

                   Display Partition Information

 Current fixed disk drive: 1

 Partition  Status  Type  Volume_Label  Mbytes  System  Usage
 C: 1          A   PRI DOS                50    FAT**     7%
    2          A   Non-DOS (Linux)       300             43%

 Total disk space is  696 Mbytes (1 Mbyte = 1048576 bytes)

 Press Esc to continue

 ---------------------------------------------------------------------

                   Display Partition Information

 Current fixed disk drive: 2

 Partition  Status  Type  Volume_Label  Mbytes  System  Usage
 D: 1          A   PRI DOS                420   FAT**    60%

 Total disk space is  696 Mbytes (1 Mbyte = 1048576 bytes)

 Press Esc to continue

 ---------------------------------------------------------------------

       ** May say FAT16 or FAT32 if you are using the OEM SR2 update.
       See Section 2.

    7. Install FreeBSD. I make sure to boot with my first hard disk
       set at "NORMAL" in the BIOS. If it is not, I will have the
       enter my true disk geometry at boot time (to get this, boot
       Windows 95 and consult Microsoft Diagnostics (MSD.EXE), or
       check your BIOS) with the parameter hd0=1416,16,63 where 1416
       is the number of cylinders on my hard disk, 16 is the number
       of heads per track, and 63 is the number of sectors per track
       on the drive.

    8. When partitioning out the hard disk, I make sure to install
       Boot Easy on the first disk. I do not worry about the second
       disk, nothing is booting off of it.

    9. When I reboot, Boot Easy should recognize my three bootable
       partitions as DOS (Windows 95), Linux, and BSD (FreeBSD).

     --------------------------------------------------------------

4 Special Considerations

   Most operating systems are very picky about where and how they are
   placed on the hard disk. Windows 95 and DOS need to be on the
   first primary partition on the first hard disk. OS/2 is the
   exception. It can be installed on the first or second disk in a
   primary or extended partition. If you are not sure, keep the
   beginning of the bootable partitions below the 1024th cylinder.

   If you install Windows 95 on an existing BSD system, it will
   "destroy" the MBR, and you will have to reinstall your previous
   boot manager. Boot Easy can be reinstalled by using the
   BOOTINST.EXE utility included in the \TOOLS directory on the
   CDROM, and via ftp. You can also re-start the installation process
   and go to the partition editor. From there, mark the FreeBSD
   partition as bootable, select Boot Manager, and then type W to
   (W)rite out the information to the MBR. You can now reboot, and
   Boot Easy should then recognize Windows 95 as DOS.

   Please keep in mind that OS/2 can read FAT and HPFS partitions,
   but not FFS (FreeBSD) or EXT2 (Linux) partitions. Likewise,
   Windows 95 can only read and write to FAT and FAT32 (see Section
   2) partitions. FreeBSD can read most filesystems, but currently
   cannot read HPFS partitions. Linux can read HPFS partitions, but
   can not write to them. Recent versions of the Linux kernel (2.x)
   can read and write to Windows 95 VFAT partitions (VFAT is what
   gives Windows 95 long file names - it is pretty much the same as
   FAT). Linux can read and write to most filesystems. Got that? I
   hope so.

     --------------------------------------------------------------

5 Examples

   (section needs work, please send your example to
   <jayrich@sysc.com>).

   FreeBSD + Windows 95: If you installed FreeBSD after Windows 95,
   you should see DOS on the Boot Easy menu. This is Windows 95. If
   you installed Windows 95 after FreeBSD, read Section 4 above. As
   long as your hard disk does not have 1024 cylinders you should not
   have a problem booting. If one of your partitions goes beyond the
   1024th cylinder however, and you get messages like "invalid system
   disk" under DOS (Windows 95) and FreeBSD will not boot, try
   looking for a setting in your BIOS called "> 1024 cylinder
   support" or "NORMAL/LBA" mode. DOS may need LBA (Logical Block
   Addressing) in order to boot correctly. If the idea of switching
   BIOS settings every time you boot up does not appeal to you, you
   can boot FreeBSD through DOS via the FBSDBOOT.EXE utility on the
   CD (It should find your FreeBSD partition and boot it.)

   FreeBSD + OS/2 + Windows 95: Nothing new here. The OS/2 boot
   manager can boot all of these operating systems, so that should
   not be a problem.

   FreeBSD + Linux: You can also use Boot Easy to boot both operating
   systems.

   FreeBSD + Linux + Windows 95: (see Section 3)

     --------------------------------------------------------------

6 Other Sources of Help

   There are many Linux HOW-TOs that deal with multiple operating
   systems on the same hard disk.

   The Linux+DOS+Win95+OS2 mini-HOWTO offers help on configuring the
   OS/2 boot manager, and the Linux+FreeBSD mini-HOWTO might be
   interesting as well. The Linux-HOWTO is also helpful.

   The Windows NT(R) Loader Hacking Guide provides good information
   on multibooting Windows NT, Windows 95, and DOS with other
   operating systems.

   And Hale Landis's "How It Works" document pack contains some good
   info on all sorts of disk geometry and booting related topics. You
   can find it at
   ftp://fission.dt.wdc.com/pub/otherdocs/pc_systems/how_it_works/allhiw.zip.

   Finally, do not overlook FreeBSD's kernel documentation on the
   booting procedure, available in the kernel source distribution (it
   unpacks to /usr/src/sys/i386/boot/biosboot/README.386BSD.

     --------------------------------------------------------------

7 Technical Details

   (Contributed by Randall Hopper, <rhh@ct.picker.com>)

   This section attempts to give you enough basic information about
   your hard disks and the disk booting process so that you can
   troubleshoot most problems you might encounter when getting set up
   to boot several operating systems. It starts in pretty basic
   terms, so you may want to skim down in this section until it
   begins to look unfamiliar and then start reading.

     --------------------------------------------------------------

  7.1 Disk Primer

   Three fundamental terms are used to describe the location of data
   on your hard disk: Cylinders, Heads, and Sectors. It is not
   particularly important to know what these terms relate to except
   to know that, together, they identify where data is physically on
   your disk.

   Your disk has a particular number of cylinders, number of heads,
   and number of sectors per cylinder-head (a cylinder-head also
   known now as a track). Collectively this information defines the
   "physical disk geometry" for your hard disk. There are typically
   512 bytes per sector, and 63 sectors per track, with the number of
   cylinders and heads varying widely from disk to disk. Thus you can
   figure the number of bytes of data that will fit on your own disk
   by calculating:

   (# of cylinders)  * (# heads)  * (63 sectors/track)  * (512
   bytes/sect)

   For example, on my 1.6 Gig Western Digital AC31600 EIDE hard disk,
   that is:

   (3148 cyl)  * (16 heads)  * (63 sectors/track)  * (512 bytes/sect)

   which is 1,624,670,208 bytes, or around 1.6 Gig.

   You can find out the physical disk geometry (number of cylinders,
   heads, and sectors/track counts) for your hard disks using ATAID
   or other programs off the net. Your hard disk probably came with
   this information as well. Be careful though: if you are using BIOS
   LBA (see Section 7.3), you can not use just any program to get the
   physical geometry. This is because many programs (e.g. MSD.EXE or
   FreeBSD fdisk) do not identify the physical disk geometry; they
   instead report the translated geometry (virtual numbers from using
   LBA). Stay tuned for what that means.

   One other useful thing about these terms. Given 3 numbers--a
   cylinder number, a head number, and a sector-within-track
   number--you identify a specific absolute sector (a 512 byte block
   of data) on your disk. Cylinders and Heads are numbered up from 0,
   and Sectors are numbered up from 1.

   For those that are interested in more technical details,
   information on disk geometry, boot sectors, BIOSes, etc. can be
   found all over the net. Query Lycos, Yahoo, etc. for boot sector
   or master boot record. Among the useful info you will find are
   Hale Landis's How It Works document pack. See the Section 6
   section for a few pointers to this pack.

   Ok, enough terminology. We are talking about booting here.

     --------------------------------------------------------------

  7.2 The Booting Process

   On the first sector of your disk (Cyl 0, Head 0, Sector 1) lives
   the Master Boot Record (MBR). It contains a map of your disk. It
   identifies up to 4 partitions, each of which is a contiguous chunk
   of that disk. FreeBSD calls partitions slices to avoid confusion
   with its own partitions, but we will not do that here. Each
   partition can contain its own operating system.

   Each partition entry in the MBR has a Partition ID, a Start
   Cylinder/Head/Sector, and an End Cylinder/Head/Sector. The
   Partition ID tells what type of partition it is (what OS) and the
   Start/End tells where it is. Table 1 lists a smattering of some
   common Partition IDs.

   Table 1. Partition IDs

   +------------------------------------------+
   | ID (hex) |          Description          |
   |----------+-------------------------------|
   | 01       | Primary DOS12 (12-bit FAT)    |
   |----------+-------------------------------|
   | 04       | Primary DOS16 (16-bit FAT)    |
   |----------+-------------------------------|
   | 05       | Extended DOS                  |
   |----------+-------------------------------|
   | 06       | Primary big DOS (> 32MB)      |
   |----------+-------------------------------|
   | 0A       | OS/2                          |
   |----------+-------------------------------|
   | 83       | Linux (EXT2FS)                |
   |----------+-------------------------------|
   | A5       | FreeBSD, NetBSD, 386BSD (UFS) |
   +------------------------------------------+

   Note that not all partitions are bootable (e.g. Extended DOS).
   Some are--some are not. What makes a partition bootable is the
   configuration of the Partition Boot Sector that exists at the
   beginning of each partition.

   When you configure your favorite boot manager, it looks up the
   entries in the MBR partition tables of all your hard disks and
   lets you name the entries in that list. Then when you boot, the
   boot manager is invoked by special code in the Master Boot Sector
   of the first probed hard disk on your system. It looks at the MBR
   partition table entry corresponding to the partition choice you
   made, uses the Start Cylinder/Head/Sector information for that
   partition, loads up the Partition Boot Sector for that partition,
   and gives it control. That Boot Sector for the partition itself
   contains enough information to start loading the operating system
   on that partition.

   One thing we just brushed past that is important to know. All of
   your hard disks have MBRs. However, the one that is important is
   the one on the disk that is first probed by the BIOS. If you have
   only IDE hard disks, it is the first IDE disk (e.g. primary disk
   on first controller). Similarly for SCSI only systems. If you have
   both IDE and SCSI hard disks though, the IDE disk is typically
   probed first by the BIOS, so the first IDE disk is the first
   probed disk. The boot manager you will install will be hooked into
   the MBR on this first probed hard disk that we have just
   described.

     --------------------------------------------------------------

  7.3 Booting Limitations and Warnings

   Now the interesting stuff that you need to watch out for.

     --------------------------------------------------------------

    7.3.1 The dreaded 1024 cylinder limit and how BIOS LBA helps

   The first part of the booting process is all done through the
   BIOS, (if that is a new term to you, the BIOS is a software chip
   on your system motherboard which provides startup code for your
   computer). As such, this first part of the process is subject to
   the limitations of the BIOS interface.

   The BIOS interface used to read the hard disk during this period
   (INT 13H, Subfunction 2) allocates 10 bits to the Cylinder Number,
   8 bits to the Head Number, and 6 bits to the Sector Number. This
   restricts users of this interface (i.e. boot managers hooked into
   your disk's MBR as well as OS loaders hooked into the Boot
   Sectors) to the following limits:

     * 1024 cylinders, max

     * 256 heads, max

     * 64 sectors/track, max (actually 63, 0 is not available)

   Now big hard disks have lots of cylinders but not a lot of heads,
   so invariably with big hard disks the number of cylinders is
   greater than 1024. Given this and the BIOS interface as is, you
   can not boot off just anywhere on your hard disk. The boot code
   (the boot manager and the OS loader hooked into all bootable
   partitions' Boot Sectors) has to reside below cylinder 1024. In
   fact, if your hard disk is typical and has 16 heads, this equates
   to:

   1024 cyl/disk  * 16 heads/disk  * 63 sect/(cyl-head)  * 512
   bytes/sector

   which is around the often-mentioned 528MB limit.

   This is where BIOS LBA (Logical Block Addressing) comes in. BIOS
   LBA gives the user of the BIOS API calls access to physical
   cylinders above 1024 though the BIOS interfaces by redefining a
   cylinder. That is, it remaps your cylinders and heads, making it
   appear through the BIOS as though the disk has fewer cylinders and
   more heads than it actually does. In other words, it takes
   advantage of the fact that hard disks have relatively few heads
   and lots of cylinders by shifting the balance between number of
   cylinders and number of heads so that both numbers lie below the
   above-mentioned limits (1024 cylinders, 256 heads).

   With BIOS LBA, the hard disk size limitation is virtually removed
   (well, pushed up to 8 Gigabytes anyway). If you have an LBA BIOS,
   you can put FreeBSD or any OS anywhere you want and not hit the
   1024 cylinder limit.

   To use my 1.6 Gig Western Digital as an example again, its
   physical geometry is:

   (3148 cyl, 16 heads, 63 sectors/track, 512 bytes/sector)

   However, my BIOS LBA remaps this to:

   (787 cyl, 64 heads, 63 sectors/track, 512 bytes/sector)

   giving the same effective size disk, but with cylinder and head
   counts within the BIOS API's range (Incidentally, I have both
   Linux and FreeBSD existing on one of my hard disks above the
   1024th physical cylinder, and both operating systems boot fine,
   thanks to BIOS LBA).

     --------------------------------------------------------------

    7.3.2 Boot Managers and Disk Allocation

   Another gotcha to watch out when installing boot managers is
   allocating space for your boot manager. It is best to be aware of
   this issue up front to save yourself from having to reinstall one
   or more of your OSs.

   If you followed the discussion in Section 7.2 about the Master
   Boot Sector (where the MBR is), Partition Boot Sectors, and the
   booting process, you may have been wondering just exactly where on
   your hard disk that nifty boot manager is going to live. Well,
   some boot managers are small enough to fit entirely within the
   Master Boot Sector (Cylinder 0, Head 0, Sector 0) along with the
   partition table. Others need a bit more room and actually extend a
   few sectors past the Master Boot Sector in the Cylinder 0 Head 0
   track, since that is typically free...typically.

   That is the catch. Some operating systems (FreeBSD included) let
   you start their partitions right after the Master Boot Sector at
   Cylinder 0, Head 0, Sector 2 if you want. In fact, if you give
   FreeBSD's sysinstall a disk with an empty chunk up front or the
   whole disk empty, that is where it will start the FreeBSD
   partition by default (at least it did when I fell into this trap).
   Then when you go to install your boot manager, if it is one that
   occupies a few extra sectors after the MBR, it will overwrite the
   front of the first partition's data. In the case of FreeBSD, this
   overwrites the disk label, and renders your FreeBSD partition
   unbootable.

   The easy way to avoid this problem (and leave yourself the
   flexibility to try different boot managers later) is just to
   always leave the first full track on your disk unallocated when
   you partition your disk. That is, leave the space from Cylinder 0,
   Head 0, Sector 2 through Cylinder 0, Head 0, Sector 63
   unallocated, and start your first partition at Cylinder 0, Head 1,
   Sector 1. For what it is worth, when you create a DOS partition at
   the front of your disk, DOS leaves this space open by default
   (this is why some boot managers assume it is free). So creating a
   DOS partition up at the front of your disk avoids this problem
   altogether. I like to do this myself, creating 1 Meg DOS partition
   up front, because it also avoids my primary DOS drive letters
   shifting later when I repartition.

   For reference, the following boot managers use the Master Boot
   Sector to store their code and data:

     * OS-BS 1.35

     * Boot Easy

     * LILO

   These boot managers use a few additional sectors after the Master
   Boot Sector:

     * OS-BS 2.0 Beta 8 (sectors 2-5)

     * The OS/2 boot manager

     --------------------------------------------------------------

    7.3.3 What if your machine will not boot?

   At some point when installing boot managers, you might leave the
   MBR in a state such that your machine will not boot. This is
   unlikely, but possible when re-FDISKing underneath an
   already-installed boot manager.

   If you have a bootable DOS partition on your disk, you can boot
   off a DOS floppy, and run:

 A:\> FDISK /MBR

   to put the original, simple DOS boot code back into the system.
   You can then boot DOS (and DOS only) off the hard drive.
   Alternatively, just re-run your boot manager installation program
   off a bootable floppy.

     --------------------------------------------------------------

           This, and other documents, can be downloaded from
                ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/.

 For questions about FreeBSD, read the documentation before contacting
                        <questions@FreeBSD.org>.
   For questions about this documentation, e-mail <doc@FreeBSD.org>.
