DISKLABEL(8)            OpenBSD System Manager's Manual           DISKLABEL(8)

NAME
     disklabel - read and write disk pack label

SYNOPSIS
     disklabel [-c | -d | -t] [-Av] [-h | -p unit] disk
     disklabel -w [-c | -d] [-Anv] disk disktype [packid]
     disklabel -e [-c | -d] [-Anv] disk
     disklabel -E [-c | -d] [-Anv] [-f tempfile] disk
     disklabel -R [-nv] disk protofile
     disklabel -N | -W [-nv] disk

     disklabel -B  [-nv] [-b boot1] [-s boot2] disk [disktype]
     disklabel -Bw [-nv] [-b boot1] [-s boot2] disk disktype [packid]
     disklabel -BR [-nv] [-b boot1] [-s boot2] disk protofile [disktype]

DESCRIPTION
     The disklabel utility can be used to install, examine, or modify the la-
     bel on a disk drive or pack.  The disk label contains information about
     disk characteristics (size, type, etc.) and the partition layout, stored
     on the disk itself.  It is used by the operating system to optimize disk
     I/O and locate the filesystems resident on the disk.

     disklabel supports 15 configurable partitions, `a' through `p', excluding
     `c'.  The `c' partition describes the entire physical disk, is automati-
     cally created by the kernel, and cannot be modified or deleted by
     disklabel.  By convention, the `a' partition of the boot disk is the root
     partition, and the `b' partition of the boot disk is the swap partition,
     but all other letters can be used in any order for any other partitions
     as desired.

     The options are as follows:

     -A      Automatically allocate all the disk space in the OpenBSD portion
             of the disk in the recommended manner.  See AUTOMATIC DISK
             ALLOCATION, below.

     -B      Install bootstrap code.  Some architectures instead require boot-
             strap code installation to be done using an installboot(8) type
             program, as described in boot(8).

     -b boot1
             Specify the single level boot program, or the primary boot pro-
             gram, depending on the system boot architecture (single or
             two-level).

     -c      Clear the system's in-core copy of the label and update it based
             on the on-disk label.

     -d      Use the default label.  This ignores any existing OpenBSD disk
             label on the disk.

     -E      Use the built-in command-driven label editor described below.

     -e      Edit an existing disk label using the editor specified in the
             EDITOR environment variable, or vi(1) if none is specified.

     -f tempfile
             Write entries to tempfile in fstab(5) format for any partitions
             for which mount point information has been specified.  The -f
             flag is only valid when used in conjunction with the -E flag.  If
             tempfile already exists, it will be overwritten.

     -h      Print partition sizes in human readable format.

     -N      Disallow writing of the pack label area on the selected disk.

     -n      Make no permanent changes to the disklabel (useful for debugging
             purposes).

     -p unit
             Print partition sizes in unit instead of sectors.  Valid units
             are b(ytes), c(ylinders), k(ilobytes), m(egabytes), g(igabytes)
             and t(erabytes).  For operations other than displaying a parti-
             tion the `%' (percent of total) and `&' (percent of free) units
             are also accepted.

     -R      Restore a disk label that was formatted in a prior operation and
             saved in an ASCII file.

     -s boot2
             On machines with a two-level bootstrap (such as i386-based
             systems), specify the secondary boot program.

     -t      Format the label as a disktab(5) entry.

     -v      Print additional information during operation (verbose mode).

     -W      Allow writing of the pack label area on the selected disk.

     -w      Write a standard label on the designated drive.

     disk    Specify the disk to operate on.  It can be specified either by
             its full pathname or an abbreviated disk form.  In its abbreviat-
             ed form, the path to the device, the `r' denoting "raw device",
             and the partition letter, can all be omitted.  For example, the
             first IDE disk can be specified as either /dev/rwd0c, /dev/wd0c,
             or wd0.

     disktype
             Specify a disktype entry from the disktab(5) database.

     packid  Specify a pack identification string for the device (see below).

     protofile
             Used with the restore option (-R) to specify a file to read an
             ASCII label from.

     The first form of the command (read) is used to examine the label on the
     named disk drive.  It will display all of the parameters associated with
     the drive and its partition layout.  The kernel's in-core copy of the la-
     bel is displayed; if the disk has no label, or the partition types on the
     disk are incorrect, the kernel may have constructed or modified the la-
     bel.

     The second form of the command (write) is used to write a standard label
     on the designated drive.  The drive parameters and partitions are taken
     from that file.  If different disks of the same physical type are to have
     different partitions, it will be necessary to have separate disktab en-
     tries describing each, or to edit the label after installation as de-
     scribed below.  The optional argument is a pack identification string, up
     to 16 characters long.  The pack ID must be quoted if it contains blanks.
     The existing label will be updated via the in-core copy and any bootstrap
     code will be unaffected.

     In the third form of the command (edit), the label is read from the in-
     core kernel copy and then supplied to an editor for changes.  If no edi-
     tor is specified in an EDITOR environment variable, vi(1) is used.  When
     the editor terminates, the formatted label is reread and used to rewrite
     the disk label.  Existing bootstrap code is unchanged.

     The built-in label editor (fourth form) provides a simple interactive la-
     bel editor.  Some commands or prompts take an optional unit.  Available
     units are `b' for bytes, `c' for cylinders, `k' for kilobytes, `m' for
     megabytes, and `g' for gigabytes.  Quantities will be rounded to the
     nearest cylinder when units are specified for sizes (or offsets).  Com-
     mands may be aborted by entering `^D' (Control-D).  Entering `^D' at the
     main `>' prompt will exit the editor.  At prompts that request a size,
     `*' may be entered to indicate the rest of the available space.  The edi-
     tor commands are as follows:

     ? [command]
                Display help message with all available commands.  A command
                may be specified to get more detailed help.  There is also
                (simple) context-sensitive help available at most prompts.

     A          Allocate all the disk space in the recommended manner.  See
                AUTOMATIC DISK ALLOCATION, below.

     a [part]   Add new partition.  This option adds a new BSD partition.  If
                no partition letter is specified (a-p), the user will be
                prompted for one.

     b          Set OpenBSD disk boundaries.  This option tells disklabel
                which parts of the disk it is allowed to modify.  This option
                is probably only useful for ports with fdisk(8) partition ta-
                bles where the ending sector in the MBR is incorrect.  The us-
                er may enter `*' at the ``Size'' prompt to indicate the entire
                size of the disk (minus the starting sector).  This is useful
                for disks larger than 8 gigabytes where the fdisk partition
                table is incapable of storing the real size.

     c [part]   Change the size of an existing partition.  If no partition is
                specified, the user will be prompted for one.  The new size
                may be in terms of the aforementioned units and may also be
                prefixed with `+' or `-' to change the size by a relative
                amount.

     D          Sets the disk label to the default values as reported by the
                kernel.  This simulates the case where there is no disk label.

     d [part]   Delete an existing partition (or `*' to delete all parti-
                tions).  If no partition is specified, the user will be
                prompted for one.

     e          Edit drive parameters.  This option is used to set the follow-
                ing parameters: disk type, a descriptive label string, sec-
                tors/track, tracks/cylinder, sectors/cylinder, number of
                cylinders, total sectors, rpm, and interleave.

     g [d | u]  Set disk geometry based on what the disk or user thinks (the
                user geometry is simply what the label said before disklabel
                made any changes).

     l [unit]   Print the disk label header.

     M          Display this manual page.

     m [part]   Modify parameters for an existing partition.  If no partition
                is specified, the user will be prompted for one.  This option
                allows the user to change the filesystem type, starting off-
                set, partition size, and mount point for the specified parti-
                tion.  If expert mode is enabled (see X below), then block
                fragment size, block size, and cylinders per group can also be
                modified.  Note that not all parameters are configurable for
                non-BSD partitions.

     n [part]   Name the mount point for an existing partition.  If no parti-
                tion is specified, the user will be prompted for one.  This
                option is only valid if disklabel was invoked with the -f
                flag.

     p [unit]   Print the current partition list.  If a unit is given, the
                size and offsets are displayed in terms of the specified unit.
                If the unit is `*' it is automatically determined by the size
                of the smallest partition.

     q          Quit the editor.  If any changes have been made, the user will
                be asked whether or not to save the changes to the on-disk la-
                bel.

     r          Recalculate free space.  This command displays all the free
                areas on the disk and the total number of free sectors.

     s [path]   Save the label to a file in ASCII format (suitable for loading
                via the -R option).  If no path is specified, the user will be
                prompted for one.

     U          Undo all changes made since entering the editor.

     u          Undo (or redo) last change.  Entering u once will undo the
                last change.  Entering it again will restore the change.

     w          Write the label to disk.  This option will commit any changes
                to the on-disk label.

     X          Toggle ``expert mode''.  By default, some settings are re-
                served for experts only (such as the block and fragment size
                on ffs partitions).

     x          Exit the editor without saving any changes to the label.

     z          Zero out the existing partition table and mountpoint informa-
                tion.  The drive parameters are not changed.

     In the restore form of the command (fifth form), the prototype file used
     to create the label should be in the same format as that produced when
     reading or editing a label.  Comments are delimited by # and newline.
     Any existing bootstrap code will be unaffected.

     The sixth form of the command (protect) is used to control write access
     to the label area of a disk so that the label cannot be inadvertently
     overwritten.  The -N and -W options are only available on architectures
     that support this feature, such as vax, hp300 and some sparc models.

     The final three forms of disklabel are used to install bootstrap code on
     machines where the bootstrap is part of the label.  The bootstrap code is
     comprised of one or two boot programs, depending on the machine.

     When installing bootstrap code with the -B flag, if the names are not ex-
     plicitly given, standard boot programs will be used.  The boot programs
     are located in /usr/mdec.  The names of the programs are taken from the
     ``b0'' and ``b1'' parameters of the disktab(5) entry for the disk if
     disktype was given and its disktab entry exists and includes those param-
     eters.  Otherwise, boot program names are derived from the name of the
     disk.  These names are of the form basenameboot for the primary (or only)
     bootstrap, and bootbasename for the secondary bootstrap; for example,
     /usr/mdec/sdboot and /usr/mdec/bootsd if the disk device is sd0.

     The first of the three boot-installation forms is used to install boot-
     strap code without changing the existing label.  It is essentially a read
     command with respect to the disk label itself and all options are related
     to the specification of the boot program as described previously.  The
     final two forms are analogous to the basic write and restore versions ex-
     cept that they will install bootstrap code in addition to a new label.

     Note that when a disk has no real BSD disklabel, the kernel creates a de-
     fault label so that the disk can be used.  This default label will in-
     clude other partitions found on the disk if they are supported on your
     architecture.  For example, on systems that support fdisk(8) partitions
     the default label will also include DOS and Linux partitions.  However,
     these entries are not dynamic, they are fixed at the time disklabel is
     run.  That means that subsequent changes that affect non-OpenBSD parti-
     tions will not be present in the default label, though they may be updat-
     ed by hand.  To see the default label, run disklabel with the -d flag.
     disklabel can then be run with the -e flag and any entries pasted as de-
     sired from the default label into the real one.

AUTOMATIC DISK ALLOCATION
     The -A option and the editor command A automatically create a disklabel
     with a set of partitions suitable for a majority of OpenBSD installa-
     tions.  Any existing OpenBSD disklabel on the disk is ignored, but native
     partitions that would normally be spoofed are preserved in the disklabel,
     and are not modified during the allocation process.

     Disk size determines the set of partitions which are created.  Each par-
     tition is allocated space between a specified minimum and maximum.  Each
     partition is allocated its minimum and remaining space is split between
     the partitions up to their maximum allowed space, which is a fixed per-
     centage.  Space left after all partitions have reached their maximum size
     is left unallocated.  The sizes below are approximations, and may vary
     from architecture to architecture.

     Disks > 6.5 Gigabytes
           /                5% of disk.  80M - 1G
           swap             5% of disk.  80M - 2x max physical memory
           /tmp             8% of disk. 120M - 4G
           /var            13% of disk.  80M - 2x size of crash dump
           /usr             2% of disk. 600M - 2G
           /usr/X11R6       3% of disk. 512M - 1G
           /usr/local       5% of disk.   2G - 6G
           /usr/src         3% of disk.   1G - 2G
           /usr/obj         3% of disk.   1G - 2G
           /home           53% of disk.   1G - 300G

     Disks > 2 Gigabytes
           /                5% of disk. 800M - 2G
           swap            10% of disk.  80M - 2x max physical memory
           /usr            78% of disk. 900M - 3G
           /home            7% of disk. 256M - 2G

     Disks > 700 Megabytes
           /               95% of disk. 700M - 4G
           swap             5% of disk.   1M - 2x max physical memory

FILES
     /etc/disklabels                   Directory for backup labels.
     /etc/disktab                      Disk description file.
     /usr/mdec/xxboot                  Primary bootstrap.
     /usr/mdec/bootxx                  Secondary bootstrap.

EXAMPLES
     Display the in-core label for sd0 as obtained via /dev/rsd0c:

           # disklabel sd0

     Create a label for sd0 based on information for ``sd2212'' found in
     /etc/disktab.  Any existing bootstrap code will be clobbered.

           # disklabel -w /dev/rsd0c sd2212 foo

     Read the on-disk label for sd0, edit it and reinstall in-core as well as
     on-disk.  Existing bootstrap code is unaffected.

           # disklabel -e sd0

     Restore the on-disk and in-core label for sd0 from information in
     mylabel.  Existing bootstrap code is unaffected.

           # disklabel -R sd0 mylabel

     Install a new bootstrap on sd0.  The boot code comes from
     /usr/mdec/sdboot and possibly /usr/mdec/bootsd.  On-disk and in-core la-
     bels are unchanged, but on some systems other information may be de-
     stroyed.  Use with care.

           # disklabel -B sd0

     Install a new label and bootstrap.  The label is derived from disktab in-
     formation for ``sd2212'' and installed both in-core and on-disk.  The
     bootstrap code comes from the file /usr/mdec/newboot.

           # disklabel -w -B /dev/rsd0c -b newboot sd2212

DIAGNOSTICS
     The kernel device drivers will not allow the size of a disk partition to
     be decreased or the offset of a partition to be changed while it is open.
     Some device drivers create a label containing only a single large parti-
     tion if a disk is unlabeled; thus, the label must be written to the `a'
     partition of the disk while it is open.  This sometimes requires the de-
     sired label to be set in two steps, the first one creating at least one
     other partition, and the second setting the label on the new partition
     while shrinking the `a' partition.

     On some machines the bootstrap code may not fit entirely in the area al-
     located for it by some filesystems.  As a result, it may not be possible
     to have filesystems on some partitions of a ``bootable'' disk.  When in-
     stalling bootstrap code, disklabel checks for these cases.  If the in-
     stalled boot code would overlap a partition of type FS_UNUSED it is
     marked as type FS_BOOT.  The newfs(8) utility will disallow creation of
     filesystems on FS_BOOT partitions.  Conversely, if a partition has a type
     other than FS_UNUSED or FS_BOOT, disklabel will not install bootstrap
     code that overlaps it.

SEE ALSO
     disklabel(5), disktab(5), scan_ffs(8)

CAVEATS
     The maximum disk and partition size is 64PB.

     On some machines, such as Sparc and Sparc64, partition tables may not ex-
     hibit the full functionality described above.

OpenBSD 4.7                      July 27, 2009                               6
