sbin/disklabel/disklabel.8

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.\"	@(#)disklabel.8	8.2 (Berkeley) 4/19/94
.\"
.Dd April 19, 1994
.Dt DISKLABEL 8
.Os
.Sh NAME
.Nm disklabel
.Nd read and write disk pack label
.Sh SYNOPSIS
.Nm ""
.Op Fl rt
.Op Fl C
.Ar disk
.Nm ""
.Fl w
.Op Fl r
.Op Fl f Ar disktab
.Ar disk Ar disktype
.Oo Ar packid Oc
.Nm ""
.Fl e
.Op Fl r
.Op Fl I
.Op Fl C
.Ar disk
.Nm ""
.Fl I
.Op Fl r
.Op Fl C
.Ar disk
.Nm ""
.Fl i
.Op Fl I
.Op Fl r
.Ar disk
.Nm ""
.Fl R
.Op Fl r
.Ar disk Ar protofile
.Nm ""
.Op Fl NW
.Ar disk
.sp
.Nm ""
.Fl B
.Op Fl f Ar disktab
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk
.Oo Ar disktype Oc
.Nm ""
.Fl w
.Fl B
.Op Fl f Ar disktab
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk Ar disktype
.Oo Ar packid Oc
.Nm ""
.Fl R
.Fl B
.Op Fl f Ar disktab
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk Ar protofile
.Oo Ar disktype Oc
.Sh DESCRIPTION
.Nm
can be used to install, examine or modify the label on a disk drive or pack.
When writing the label, it can be used
to change the drive identification,
the disk partitions on the drive,
or to replace a damaged label.
On some systems,
.Nm
can be used to install bootstrap code as well.
.Pp
There are several forms of the command that read (display), install or edit
the label on a disk.
Each form has an additional option,
.Fl r ,
which 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 installed
on a system; it must be used when first installing a label on a disk.
Any special effects of the
.Fl r
flag are described with the affected commands.
.Pp
The read and install forms also support the
.Fl B
option to install bootstrap code on some platforms,
e.g. hp300, vax, and arm32.
The
.Fl B
option is not supported on all platforms.
These variants are described later.
.Pp
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
.Fl r
flag is given,
the kernel's in-core copy of the label 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 label.
If the
.Fl r
flag is given, the label from the raw disk will be displayed rather
than the in-core label.
If the
.Fl t
flag is given, then the label will be formatted as a
.Xr disktab 5
entry.
.Pp
The second form of the command, with the
.Fl w
flag, is used to write a standard label on the designated drive.
The required arguments to
.Nm
are the drive to be labelled (e.g. sd0), and
the drive type as described in the
.Xr disktab 5
file.
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 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 disk does not already have a label, the
.Fl r
flag must be used.
In either case, the kernel's in-core label is replaced.
.Pp
An alternate
.Xr disktab 5
file may be specified with the
.Fl f Ar disktab
option.
.Pp
An existing disk label may be edited by using the
.Fl e
flag.
The label is formatted and then supplied to an editor for changes.
If no editor is specified in an
.Ev EDITOR
environment variable,
.Xr vi 1
is used.
When the editor terminates, the formatted label is reread
and used to rewrite the disk label.
.Pp
Labels can also created interactively using the
.Fl i
flag.
.Pp
The
.Fl C
flag causes the partition offset and size values to be displayed in
.Aq cylinder/track/sector
format. Note that, regardless of whether
.Fl C
was specified, this format is always accepted by
.Nm
on input with either the
.Fl e
or
.Fl R
flag.
.Pp
With the
.Fl R
flag,
.Nm
is capable of restoring a disk label that was formatted
in a prior operation and saved in an ascii file.
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
.Ar \&#
and newline.
.Pp
The
.Fl NW
flags for
.Nm
explicitly disallow and
allow, respectively, writing of the pack label area on the selected disk.
.Pp
The final three forms of
.Nm
are used to install bootstrap code on machines where the bootstrap is part
of the label.
The bootstrap code is composed of one or two boot programs depending on
the machine.
The
.Fl B
option is used (on some platforms only, see above) to denote that
bootstrap code is to be installed.
The
.Fl r
flag is implied by
.Fl B
and never needs to be specified.
The name of the boot program(s) to be installed can be selected in a
variety of ways.
First, the names can be specified explicitly via the
.Fl b
and
.Fl s
flags.
On machines with only a single level of boot program,
.Fl b
is the name of that program.
For machines with a two-level bootstrap,
.Fl b
indicates the primary boot program and
.Fl s
the secondary boot program.
If the names are not explicitly given, standard boot programs will be used.
The boot programs are located in
.Pa /usr/mdec .
The names of the programs are taken from the ``b0'' and ``b1'' parameters
of the
.Xr disktab 5
entry for the disk if
.Ar 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
.Pa basename Ns boot
for the primary (or only) bootstrap, and
.Pf boot Pa basename
for the secondary bootstrap;
for example,
.Pa /usr/mdec/sdboot
and
.Pa /usr/mdec/bootsd
if the disk device is
.Em sd0 .
.Pp
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.
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /etc/disktab
.It Pa /usr/mdec/ Ns Em xx Ns boot
.It Pa /usr/mdec/boot Ns Em xx
.El
.Sh EXAMPLES
.Dl disklabel sd0
.Pp
Display the in-core label for sd0 as obtained via
.Pa /dev/rsd0c .
.Pp
.Dl disklabel -w -r /dev/rsd0c sd2212 foo
.Pp
Create a label for sd0 based on information for ``sd2212'' found in
.Pa /etc/disktab ,
using
.Pa foo
as the disk pack label.
Any existing bootstrap code will be clobbered.  If you do not have an
entry for your disk in
.Pa /etc/disktab ,
you can use this style to put
an initial label onto a new disk.  Then dump the label to a file (using
.Em disklabel sd0 \*[Gt]
.Em protofile ) ,
editing the file, and replacing the label with
.Em disklabel -R sd0
.Em protofile .
.Pp
.Dl disklabel -e -r sd0
.Pp
Read the on-disk label for sd0, edit it and reinstall in-core as well
as on-disk.
Existing bootstrap code is unaffected.
.Pp
.Dl disklabel -e -I sd0
.Pp
As previous, but don't fail if there was no label on the disk yet;
provide some default values instead.
.Pp
.Dl disklabel -i -I sd0
.Pp
As previous, only use the built-in interactive editor.
.Pp
.Dl disklabel -R sd0 mylabel
.Pp
Restore the on-disk and in-core label for sd0 from information in
.Pa mylabel .
Existing bootstrap code is unaffected.
.Pp
.Dl disklabel -B sd0
.Pp
Install a new bootstrap on sd0 (only for platforms which support the
.Fl B
option, see above).
The boot code comes from
.Pa /usr/mdec/sdboot
and possibly
.Pa /usr/mdec/bootsd .
On-disk and in-core labels are unchanged.
.Pp
.Dl disklabel -w -B /dev/rsd0c -b newboot sd2212
.Pp
Install a new label and bootstrap (on platforms which support the
.Fl B
option, see above).
The label is derived from disktab information for ``sd2212'' and
installed both in-core and on-disk.
The bootstrap code comes from the file
.Pa /usr/mdec/newboot .
.Pp
.Dl disklabel -R -r sd0 \*[Lt]protofile\*[Gt]
.Pp
Install a new label and bootstrap on a disk, from a prototype label
file.  This is a good way to install a label on a previously unlabeled
disk for which no entry appears in
.Pa  /etc/disktab ,
if you create the
prototype file by dumping some other disk's label to a file and editing
it appropriately (total size, partition offsets, types, etc.)
.Sh 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 partition
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 desired 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.
.Pp
On some machines the bootstrap code may not fit entirely in the area
allocated for it by some filesystems.
As a result, it may not be possible to have filesystems on some partitions
of a ``bootable'' disk.
When installing bootstrap code,
.Nm
checks for these cases.
If the installed boot code would overlap a partition of type FS_UNUSED
it is marked as type FS_BOOT.
The
.Xr 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,
.Nm
will not install bootstrap code that overlaps it.
.Sh SEE ALSO
.Xr disklabel 5 ,
.Xr disktab 5 ,
.Xr fdisk 8 ,
.Xr installboot 8 ,
.Xr mbrlabel 8
.Sh BUGS
If the disk partition is not specified in the disk name
(i.e. ``xy0'' instead of ``/dev/rxy0c''),
.Nm
will construct the full pathname of the disk and use
the ``a'' partition on the tahoe,
the ``d'' partition on i386 or hpcmips or arc, and
the ``c'' partition on all others.
.Pp
On the sparc, sparc64, sun2 and sun3
.Nx
systems, the size of each partition must be a multiple of the number
of sectors per cylinder (i.e. each partition must be an integer
number of cylinders), or the boot ROMs will declare the label
invalid and fail to boot the system.
.Pp
In addition, the
.Fl r
option should never be used on a sparc, sparc64, sun2 or sun3 system
boot disk - the
.Nx
kernel translates the
.Nx
disk label into a SunOS compatible format (which is required by the
boot PROMs) when it writes the label. Using the
.Fl r
causes
.Nm
to write directly to disk, and bypass the format translation.
This will result in a disk label that the PROMs will not recognize,
and that therefore cannot be booted from.