MirBSD manpage: disklabel(8)

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


     disklabel - read and write disk pack label


     disklabel [-c | -d | -r | -t] [-v] [-p unit] disk
     disklabel -w [-c | -d | -r] [-nv] disk disktype [packid]
     disklabel -e [-c | -d | -r] [-nv] disk
     disklabel -E [-c | -d | -r] [-nv] [-f tempfile] disk
     disklabel -R [-nrv] 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]


     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 slice 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:

     -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-

     -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

     -d      Use the default label. This ignores any existing MirBSD slices 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.

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

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

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

     -p unit
             Print slice sizes and offsets in unit instead of sectors. Valid
             units are b(ytes), c(ylinders), k(ilobytes), m(egabytes) and
             g(igabytes). For operations other than displaying a slice the '%'
             (percent of total) and '&' (percent of free) units are also ac-

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

     -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.

     -s      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 abbreviated
             form, the path to the device, the 'r' denoting "raw device", and
             the slice, can all be omitted. For example, the first IDE disk
             can be specified as either /dev/rwd0c, /dev/wd0c, or wd0.

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

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

             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 slice layout. Unless the -r flag is given, the kernel's
     in-core copy of the label is displayed; if the disk has no label, or the
     slice 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 slices are taken from
     that file. If different disks of the same physical type are to have dif-
     ferent slices, it will be necessary to have separate disktab entries
     describing each, or to edit the label after installation as described
     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 bootstrap
     will be written directly. A side-effect of this is that any existing
     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 al-
     ready 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 (fourth form) is only intended for new
     disks as it will move slices 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).
     Commands 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 [part]   Add new slice. This option adds a new BSD slice. If no letter
                is specified (a-p), the user will be prompted for one.

     b          Set MirBSD 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 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 in-
                capable of storing the real size.

     c [part]   Change the size of an existing slice. If no slice is speci-
                fied, 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 slice (or '*' to delete all slices). If no
                slice is specified, the user will be prompted for one. The 'c'
                slice cannot be deleted.

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

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

     M          Display this manual page.

     m [part]   Modify parameters for an existing slice. If no slice is speci-
                fied, the user will be prompted for one. This option allows
                the user to change the filesystem type, starting offset, size,
                and mount point for the specified slice. If expert mode is en-
                abled (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 slices.

     n [part]   Name the mount point for an existing slice. If no slice 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 disk label. If a unit is given, the size and
                offsets are displayed in terms of the specified unit.

     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-

     r          Recalculate free space. This option should really not be
                necessary under normal circumstances.

     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 (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 reserved
                for experts only (such as the block and fragment size on ffs

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

     z          Zeroes out the existing disklabel, leaving only the 'c' slice.
                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. As
     with -w, any existing bootstrap code will be clobbered if -r is specified
     and will be unaffected otherwise.

     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 parameters.
     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
     bootstrap 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
     except 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 include
     other slices found on the disk if they are supported on your architec-
     ture. For example, on systems that support fdisk(8) partitions the de-
     fault 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-MirBSD slices will not
     be present in the default label, though they may be updated 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 desired from the de-
     fault label into the real one.


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


     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. (Normally
     you do not want to use the -r flag though.)

           # disklabel -w -r /dev/rsd0c sd2212 foo

     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 -e -r 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 labels are unchanged,
     but on some systems other information may be destroyed. 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


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

     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 slices of a "bootable" disk. When installing
     bootstrap code, disklabel checks for these cases. If the installed boot
     code would overlap a slice of type FS_UNUSED it is marked as type
     FS_BOOT. The newfs(8) utility will disallow creation of filesystems on
     FS_BOOT slices. Conversely, if a slice has a type other than FS_UNUSED or
     FS_BOOT, disklabel will not install bootstrap code that overlaps it.


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


     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, disklabels may not exhibit the full
     functionality that is described above.

     disklabel only supports up to a maximum of 15 slices, 'a' through 'p',
     excluding 'c'. The 'c' slice is reserved for the entire physical disk. By
     convention, the 'a' slice of the boot disk is the root filesystem, and
     the 'b' slice of the boot disk is the swap partition, but all other
     letters can be used in any order for any other slices as desired.


     When a disk name is given without a full pathname, the constructed device
     name uses the 'c' slice. In -E mode, disklabel is far too quick to shuf-
     fle slices around; it should keep a free block list and only move slices
     around with the user's permission.

MirBSD #10-current             October 27, 1997                              5

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