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

NAME
     disklabel - read and write disk pack label

SYNOPSIS
     disklabel [-n] [-cd | -r] [-t] [-v] disk
     disklabel -w [-n] [-cd | -r] [-v] disk disktype [packid]
     disklabel -e [-n] [-cd | -r] [-v] disk
     disklabel -E [-f tempfile] [-n] [-cd | -r] [-v] disk
     disklabel -R [-r] [-n] [-v] disk protofile
     disklabel [-NW] [-n] [-v] disk

     disklabel -B [-n] [-v] [-b boot1 [-s boot2]] disk [disktype]
     disklabel -w -B [-n] [-v] [-b boot1 [-s boot2]] disk disktype [packid]
     disklabel -R -B [-n] [-v] [-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.

     The options are as follows:

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

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

     -r      Causes the label to be read from or written to the disk directly,
             rather than going through the system's in-core copy of the label.
             This option may allow a label to be installed on a disk without
             kernel support for a label, such as when labels are first in-
             stalled on a system.  This flag does not work on a number of ar-
             chitectures, thus it is not considered the right way to put a new
             label on a disk.  Its use is discouraged.

     -B      Install bootstrap code.  The -r flag is implied by -B and never
             needs to be specified.

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

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

     -d      Use the default label.  This ignores any existing OpenBSD parti-
             tions on the disk.  Note that this option will only work for
             disks that are capable of reporting their geometry, such as SCSI,
             IDE, and ESDI.  May not be used in conjunction with the -r flag.

     -c      Clear the system's in-core copy of the label and update it based
             on the on-disk label.  May not be used in conjunction with the -r
             flag.

     -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.


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

     -w      Write a standard label on the designated drive.

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

     -E      Use a simple initial label editor, using the command-driven
             built-in editor described below.

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

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

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

     The first form of the command (read) is used to examine the label on the
     named disk drive (e.g., sd0 or /dev/rsd0c). It will display all of the
     parameters associated with the drive and its partition layout.  Unless
     the -r flag is given, the kernel's in-core copy of the label is dis-
     played; if the disk has no label, or the partition types on the disk are
     incorrect, the kernel may have constructed or modified the label.

     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.
     If the -r flag is given, the disk sectors containing the label and boot-
     strap will be written directly.  A side-effect of this is that any exist-
     ing bootstrap code will be overwritten and the disk rendered unbootable.
     If -r is not specified, the existing label will be updated via the in-
     core copy and any bootstrap code will be unaffected.  If the disk does
     not already have a label, the -r flag must be used.  In either case, the
     kernel's in-core label is replaced.

     In the third form of the command (edit), the label is read from the in-
     core kernel copy, or directly from the disk if the -r flag is also given.
     The label is formatted and then supplied to an editor for changes.  If no
     editor 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 regardless
     of whether -r was specified.

     The initial label editor mode is only intended for new disks as it will
     move partitions around as necessary to maintain a contiguous pool of free
     blocks.  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.  You may
                specify a command for which to get more detailed help.  There
                is also (simple) context-sensitive help available at most
                prompts.



     M          Display this manual page.

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

     p [unit]   Print the current disk label.  If a unit is given, the size
                and offsets are displayed in terms of the specified unit.

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

     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 partition tables
                where the ending sector in the MBR is incorrect.  The user 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.

     r          Recalculate free space.  This option should really not be nec-
                essary under normal circumstances.

     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.

     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 [part]   Delete an existing partition (or `*' to delete all parti-
                tions).  If no partition is specified, the user will be
                prompted for one.  You may not delete the `c' partition.

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

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

     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, block fragment size, block size, and
                cylinders per group for the specified partition (not all pa-
                rameters 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.

     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.

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


                to the on-disk label.

     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.

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

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

     z          Zeroes out the existing partition table, leaving only the
                ``c'' partition.  The drive parameters are not changed.

     In the restore form of the command, the prototype file used to create the
     label should be in the same format as that produced when reading or edit-
     ing a label.  Comments are delimited by # and newline.  As with -w, any
     existing bootstrap code will be clobbered if -r is specified and will be
     unaffected otherwise.

     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 installting bootstrap code with the -B flag, if the names are not
     explicitly 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.

EXAMPLES
           disklabel sd0

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

           disklabel -w -r /dev/rsd0c sd2212 foo

     Create a label for sd0 based on information for ``sd2212'' found in
     /etc/disktab. Any existing bootstrap code will be clobbered.  (Normally
     you do not want to use the -r flag though.)

           disklabel -e -r sd0

     Read the on-disk label for sd0, edit it and reinstall in-core as well as
     on-disk.  (Normally you do not want to use the -r flag though.)  Existing
     bootstrap code is unaffected.

           disklabel -R sd0 mylabel

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

           disklabel -B sd0

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

     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.

FILES
     /etc/disktab
     /usr/mdec/xxboot
     /usr/mdec/bootxx

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

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.

NOTES
     On i386 machines, installboot(8) is normally used to install boot code.
     The -B option to disklabel can still be used to install old style boot
     code, but this usage is deprecated.

     On some machines, such as the sparc and amiga, partition tables may not
     exhibit the full functionality that is described above.

BUGS
     When a disk name is given without a full pathname, the constructed device
     name uses the `a' partition on the tahoe, the `c' partition on all oth-
     ers.  In -E mode, disklabel is far too quick to shuffle partitions
     around; it should keep a free block list and only move partitions around
     with the user's permission.  Also, in -E mode, partitions outside the
     OpenBSD portion of the disk should be changeable.

OpenBSD 2.9                    October 27, 1997                              5
