                 Formatting Media For Use With FreeBSD

A Tutorial

  Doug White

       <dwhite@resnet.uoregon.edu>
     

   March 1997

   FreeBSD is a registered trademark of the FreeBSD Foundation.

   Iomega, Zip, and Jaz are either registered trademarks or
   trademarks of Iomega Corporation in the United States and/or other
   countries.

   Motif, OSF/1, and UNIX are registered trademarks and IT DialTone
   and The Open Group are trademarks of The Open Group in the United
   States and 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 describes how to slice, partition, and format hard
   disk drives and similar media for use with FreeBSD. The examples
   given have been tested under FreeBSD 2.2 and should work for other
   releases. The text has been updated for FreeBSD version 4.

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

1 Introduction & Definitions

  1.1 Overview

   Successfully adding disks to an existing system is the mark of an
   experienced system administrator. Slicing, partitioning, and
   adding disks requires a careful dance of proper command and name
   syntax. One slipped finger and an entire disk could disappear in
   seconds. This document is written in an attempt to simplify this
   process and avoid accidents. Thankfully, enhancements to existing
   tools (notably sysinstall) have greatly improved this process in
   recent releases of FreeBSD.

   There are two possible modes of disk formatting:

     * compatibility mode: Arranging a disk so that it has a slice
       table for use with other operating systems.

     * dedicated mode, sometimes called dangerously dedicated mode:
       Formatting a disk with no slice table. This makes the process
       of adding disks easier, however non-FreeBSD operating systems
       may not accept the disk. The term dangerously refers to the
       danger that the system may not recognize a disk formatted in
       this manner.

   For most cases, dedicated mode is the easiest to set up and use in
   existing systems, as a new disk is usually dedicated entirely to
   FreeBSD. However, compatibility mode insures optimum
   interoperability with future installations at a cost of increased
   complexity.

   In addition to selecting the mode, two methods of slicing the disk
   are available. One is using the system installation tool
   /stand/sysinstall. 2.1.7-RELEASE and later versions of sysinstall
   contain code to ease setup of disks during normal system
   operation, mainly allowing access to the Label and Partition
   editors and a Write feature which will update just the selected
   disk and slice without affecting other disks. The other method is
   running the tools manually from a root command line. For dedicated
   mode, only three or four commands are involved while sysinstall
   requires some manipulation.

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  1.2 Definitions

   UNIX(R) disk management over the centuries has invented many new
   definitions for old words. The following glossary covers the
   definitions used in this document and (hopefully) for FreeBSD in
   general.

     * compatibility mode: Arranging a disk so that it has a slice
       table for use with other operating systems. Oppose dedicated
       mode.

     * (dangerously) dedicated mode: Formatting a disk with no slice
       table. This makes the process of adding disks easier, however
       non-FreeBSD operating systems may not accept the disk. Oppose
       compatibility mode.

     * disk: Hard disks, CDROMs, magneto-optical devices and
       Zip(R)/Jaz(R) removable media are example of storage devices
       commonly used today. The basic principle of the way these work
       is that one or more spinning disks spin by a motor, while a
       head, moving on a radial path close to the disks, reads from
       or writes data to the disk. Writing is done by modifying some
       physical properties of the disk (magnetic flow, reflectivity,
       etc.) while reading is done by "detecting" changes to the same
       physical properties of the disk.

     * slice: A division of a disk. Up to four slices are permitted
       on one disk in the PC standard. Slices are composed of
       contiguous sectors. Slices are recorded in a "slice table"
       used by the system BIOS to locate bootable partitions. The
       slice table is usually called the "partition table" in DOS
       parlance. Maintained by the fdisk utility.

     * partition: A division of a slice. Usually used in reference to
       divisions of the FreeBSD slice of a disk. Each filesystem and
       swap area on a disk resides in a partition. Maintained using
       the disklabel utility.

     * sector: Smallest subdivision of a disk. One sector usually
       represents 512 bytes of data.

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  1.3 Warnings & Pitfalls

   Building disks is not something to take lightly. It is quite
   possible to destroy the contents of other disks in your system if
   the proper precautions are not taken.

   Check your work carefully. It is very simple to destroy the
   incorrect disk when working with these commands. When in doubt
   consult the kernel boot output for the proper device.

   Needless to say, we are not responsible for any damage to any data
   or hardware that you may experience. You work at your own risk!

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  1.4 Zip, Jaz, and Other Removables

   Removable disks can be formatted in the same way as normal hard
   disks. It is essential to have the disk drive connected to the
   system and a disk placed in the drive during startup, so the
   kernel can determine the drive's geometry. Check the dmesg output
   and make sure your device and the disk's size is listed. If the
   kernel reports

 Can't get the size

   then the disk was not in the drive. In this case, you will need to
   restart the machine before attempting to format disks.

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2 Formatting Disks in Dedicated Mode

  2.1 Introduction

   This section details how to make disks that are totally dedicated
   to FreeBSD. Remember, dedicated mode disks sometimes cannot be
   booted by the PC architecture.

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

  2.2 Making Dedicated Mode Disks using Sysinstall

   /stand/sysinstall, the system installation utility, has been
   expanded in recent versions to make the process of dividing disks
   properly a less tiring affair. The fdisk and disklabel editors
   built into sysinstall are GUI tools that remove much of the
   confusion from slicing disks. For FreeBSD versions 2.1.7 and
   later, this is perhaps the simplest way to slice disks.

    1. Start sysinstall as root by typing

 # /stand/sysinstall

       from the command prompt.

    2. Select Index.

    3. Select Partition.

    4. Select the disk to edit with arrow keys and SPACE.

    5. If you are using this entire disk for FreeBSD, select A.

    6. When asked if you still want to do this, answer Yes.

    7. Select Write.

    8. When warned about writing on installed systems, answer Yes.

    9. When asked about installing a boot loader, select None to
       leave the Master Boot Record untouched. This is only needed on
       a new install of FreeBSD unless the disk will be placed into
       another machine.

   10. Press ENTER on the message stating "Wrote FDISK partition
       information out successfully".

   11. Quitthe FDISK Editor and ESCAPE back to the Index menu.

   12. Select Label from the Index menu.

   13. Label as desired. For a single partition, enter C to Create a
       partition, accept the default size, partition type Filesystem,
       and a mountpoint (which is not used).

   14. Enter W when done and confirm to continue. The filesystem will
       be newfs'd for you, unless you select otherwise (for new
       partitions you will want to do this!). You will get the error:

 Error mounting /mnt/dev/ad2s1e on /mnt/blah : No such file or directory

       Ignore.

   15. Exit out by repeatedly pressing ESCAPE.

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  2.3 Making Dedicated Mode Disks Using the Command Line

   Execute the following commands, replacing ad2 with the disk name.

 # dd if=/dev/zero of=/dev/ad2 count=2
 # disklabel /dev/ad2 | disklabel -B -R -r ad2 /dev/stdin
 We only want one partition, so using slice 'c' should be fine:
 # newfs /dev/ad2c

   If you need to edit the disklabel to create multiple partitions
   (such as swap), use the following:

 # dd if=/dev/zero of=/dev/ad2 count=2
 # disklabel /dev/ad2 > /tmp/label
 Edit disklabel to add partitions:
 # vi /tmp/label
 # disklabel -B -R -r ad2 /tmp/label
 newfs partitions appropriately

   Your disk is now ready for use.

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3 Making Compatibility Mode Disks

  3.1 Introduction

   The command line is the easiest way to make dedicated disks, and
   the worst way to make compatibility disks. The command-line fdisk
   utility requires higher math skills and an in-depth understanding
   of the slice table, which is more than most people want to deal
   with. Use sysinstall for compatibility disks, as described below.

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

  3.2 Making Compatibility Mode Disks Using Sysinstall

    1. Start sysinstall as root by typing

 # /stand/sysinstall

       from the command prompt.

    2. Select Index.

    3. Select Partition.

    4. Select the disk to edit with arrow keys and SPACE.

    5. If you are using this entire disk for FreeBSD, select A.

    6. When asked:

 Do you want to do this with a true partition entry so as to remain
 cooperative with any future possible operating systems on the
 drive(s)?

       answer yes.

    7. Select Write.

    8. When asked to install the boot manager, select None with SPACE
       then hit ENTER for OK.

    9. Quit the FDISK Editor.

   10. You will be asked about the boot manager, select None again.

   11. Select Label from the Index menu.

   12. Label as desired. For a single partition, accept the default
       size, type filesystem, and a mountpoint (which is not used).

   13. The filesystem will be newfs'd for you, unless you select
       otherwise (for new partitions you will want to do this!). You
       will get the error:

 Error mounting /mnt/dev/ad2s1e on /mnt/blah : No such file or directory

       Ignore.

   14. Exit out by repeatedly pressing ESCAPE.

   Your new disk is now ready for use.

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4 Other Disk Operations

  4.1 Adding Swap Space

   As a system grows, its need for swap space can also grow. Although
   adding swap space to existing disks is very difficult, a new disk
   can be partitioned with additional swap space.

   To add swap space when adding a disk to a system:

    1. When partitioning the disk, edit the disklabel and allocate
       the amount of swap space to add in partition `b' and the
       remainder in another partition, such as `a' or `e'. The size
       is given in 512 byte blocks.

    2. When newfsing the drive, do NOT newfs the `c' partition.
       Instead, newfs the partition where the non-swap space lies.

    3. Add an entry to /etc/fstab as follows:

 /dev/ad0b                       none            swap    sw 0 0
            

       Change /dev/ad0b to the device of the newly added space.

    4. To make the new space immediately available, use the swapon
       command.

 # swapon /dev/da0b
 swapon:  added /dev/da0b as swap space

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  4.2 Copying the Contents of Disks

   Submitted By: Renaud Waldura (<renaud@softway.com>)

   To move file from your original base disk to the fresh new one,
   do:

 # mount /dev/ad2 /mnt
 # pax -r -w -p e /usr/home /mnt
 # umount /mnt
 # rm -rf /usr/home/*
 # mount /dev/ad2 /usr/home

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  4.3 Creating Striped Disks using CCD

   Commands Submitted By: Stan Brown (<stanb@awod.com>)

   The Concatenated Disk Driver, or CCD, allows you to treat several
   identical disks as a single disk. Striping can result in increased
   disk performance by distributing reads and writes across the
   disks. See the ccd(4) and ccdconfig(8) manual pages or the CCD
   Homepage for further details.

   You no longer need to build a special kernel to run ccd. When you
   run ccdconfig, it will load the KLD for you if the kernel does not
   contain CCD support.

   You build CCDs on disk partitions of type 4.2BSD. If you want to
   use the entire disk, you still need to create a new partition. For
   example, disklabel -e might show:

 #        size   offset    fstype   [fsize bsize bps/cpg]
   c: 60074784        0    unused        0     0     0   # (Cyl.    0 - 59597)

   You should not use partition c for the CCD, since it is of type
   unused. Instead, create a new partition of exactly the same size,
   but with type 4.2BSD:

 #        size   offset    fstype   [fsize bsize bps/cpg]
   c: 60074784        0    unused        0     0     0   # (Cyl.    0 - 59597)
    e: 60074784        0    4.2BSD        0     0     0   # (Cyl.    0 - 59597)

   To create a new CCD, execute the following commands. This
   describes how to add three disks together; simply add or remove
   devices as necessary. Remember that the disks to be striped must
   be identical.

 # cd /dev ; sh MAKEDEV ccd0

 # disklabel -r -w da0 auto
 # disklabel -r -w da1 auto
 # disklabel -r -w da2 auto

 # disklabel -e da0
 Add partition e with type 4.2BSD
 # disklabel -e da1
 Add partition e with type 4.2BSD
 # disklabel -e da2
 Add partition e with type 4.2BSD

 # ccdconfig ccd0 273 0 /dev/da0e /dev/da1e /dev/da2e

 # newfs /dev/ccd0c

   The value 273 is the stripe size. This is the number of disk
   sectors (of 512 bytes each) in each block of data on the CCD. It
   should be at least 128 kB, and it should not be not be a power of
   2.

   Now you can mount and use your CCD by referencing device
   /dev/ccd0c.

   A more powerful and flexible alternative to CCD is Vinum. See the
   Vinum Project home page for further details.

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5 Credits

   The author would like to thank the following individuals for their
   contributions to this project:

     * Darryl Okahata (<darrylo@hpnmhjw.sr.hp.com>) for his simple
       dedicated mode setup documentation which I have used
       repeatedly on FreeBSD-questions.

     * Jordan K. Hubbard <jkh@FreeBSD.org> for making sysinstall
       useful for this type of task.

     * John Fieber (<jfieber@indiana.edu>) for making information and
       examples of the DocBook DTD on which this document is based.

     * Greg Lehey <grog@FreeBSD.org> for checking my work and
       pointing out inaccuracies, as well as miscellaneous support.

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           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>.
