path: root/sbin/disklabel/disklabel.8

.\"	$OpenBSD: disklabel.8,v 1.16 1998/04/08 03:00:44 millert Exp $
.\"	$NetBSD: disklabel.8,v 1.9 1995/03/18 14:54:38 cgd Exp $
.\"
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.\"	@(#)disklabel.8	8.2 (Berkeley) 4/19/94
.\"
.Dd October 27, 1997
.Dt DISKLABEL 8
.Os BSD 4.2
.Sh NAME
.Nm disklabel
.Nd read and write disk pack label
.Sh SYNOPSIS
.Nm disklabel
.Op Fl r
.Op Fl n
.Op Fl t
.Ar disk
.Nm disklabel
.Fl w
.Op Fl r
.Op Fl n
.Ar disk Ar disktype
.Oo Ar packid Oc
.Nm disklabel
.Fl e
.Op Fl r
.Op Fl n
.Ar disk
.Nm disklabel
.Fl E
.Op Fl r
.Op Fl n
.Ar disk
.Nm disklabel
.Fl R
.Op Fl r
.Op Fl n
.Ar disk Ar protofile
.Nm disklabel
.Op Fl NW
.Op Fl n
.Ar disk
.sp
.Nm disklabel
.Fl B
.Op Fl n
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk
.Oo Ar disktype Oc
.Nm disklabel
.Fl w
.Fl B
.Op Fl n
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk Ar disktype
.Oo Ar packid Oc
.Nm disklabel
.Fl R
.Fl B
.Op Fl n
.Oo
.Fl b Ar boot1
.Op Fl s Ar boot2
.Oc
.Ar disk Ar protofile
.Oo Ar disktype Oc
.Sh DESCRIPTION
.Nm Disklabel
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 disklabel
can be used to install bootstrap code as well.
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.
The specific effect of
.Fl r
is described under each command.
The read and install forms also support the
.Fl B
option to install bootstrap code.
These variants are described later.
.Pp
In all cases you can specify
.Fl n
to operate in no change mode to avoid committing any permanent changes.
.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 disklabel
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
.Fl 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
.Fl 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
.Fl r
flag must be used.
In either case, the kernel's in-core label is replaced.
.Pp
An existing disk label may be edited by using the
.Fl e
flag.
The label is read from the in-core kernel copy,
or directly from the disk if the
.Fl r
flag is also given.
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.
Existing bootstrap code is unchanged regardless of whether
.Fl r
was specified.
.Pp
With the
.Fl R
flag,
.Nm disklabel
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.
As with
.Fl w ,
any existing bootstrap code will be clobbered if
.Fl r
is specified and will be unaffected otherwise.
.Pp
The
.Fl NW
flags for
.Nm disklabel
explicitly disallow and
allow, respectively, writing of the pack label area on the selected disk.
.Pp
The
.Fl E
flag to
.Nm disklabel
will drop you into a simple initial label editor.  This mode is
only intended for new disks as it will move partitions around as
necessary to maintain a contiguous pool of free blocks.  Some command
or prompts take an optional unit.  Available units are 'b' for
bytes, 'c' for cylinders, 'k' for kilobytes, 'm' for megabytes, '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 editor commands are as follows:
.Bl -tag -width "p [unit] "
.It ?
Display help message with all available commands.  There is (simple)
context-sensitive help available at most prompts.
.It M
Display this manual page.
.It u
Undo (or redo) last change.  Undo will reset the disklabel to the
state before the last command that modified it.
.\" bad sentence!
.It p Op unit
Print the current disk label.  If a
.Em unit
is given, the size and offsets are displayed in terms of the
specified unit.
.It e
Edit drive parameters.  This option is used to set the following
parameters:  bytes/sector, sectors/track, tracks/cylinder,
sectors/cylinder, number of cylinders, total sectors on the disk,
rpm, disk type, and a descriptive label string.
.It b
Set OpenBSD disk boundaries.  This option tells
.Nm disklabel
which parts of the disk it is allow 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 large disks where the
fdisk partition table is incapable if storing the real size.
.\" What is this limit?  [somewhere between 8 and 9 gig]
.It r
Recalculate free space.  This option should really not be necessary
under normal circumstances.
.It a Op part
Add new partition.  This option adds a new BSD partition.  If no
partion letter is specified (a-p), the user will be prompted for
one.
.It c Op part
Change the size of an existing partition.  If no parition 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.
.It d Op part
Delete an existing partition.  If no parition is specified, the
user will be prompted for one.
.It m Op part
Modify parameters for an existing partition.  If no parition is
specified, the user will be prompted for one.  This option allows
the user to change the filesystem type, starting offset, parition
size, block fragment size, block size, and cylinders per group for
the specified partition (not all parameters are configurable for
non-BSD partitions).
.It s Op path
Save the label to a file in ascii format (suitable for loading via
the
.Op -R
option).  If no path is specified, the user will be prompted for
one.
.It w
Write the label to disk.  This option will commit any changes to
the on-disk label.
.It 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 label.
.It x
Exit the editor without saving any changes to the label.
.El
.Pp
The final three forms of
.Nm disklabel
are used to install boostrap 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.  The
.Fl B
option is used 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 .
Any existing bootstrap code will be clobbered.  (Normally you do
not want to use the -r flag though.)
.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.  (Normally you do not want to use the -r flag
though.)  Existing bootstrap code is unaffected.
.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.  The boot code comes from
.Pa /usr/mdec/sdboot
and possibly
.Pa /usr/mdec/bootsd .
On-disk and in-core labels are unchanged, but on some systems other
information may be destroyed.  Use with care.
.Pp
.Dl disklabel -w -B /dev/rsd0c -b newboot sd2212
.Pp
Install a new label and bootstrap.  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 .
.Sh SEE ALSO
.Xr disktab 5 ,
.Xr disklabel 5
.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 disklabel
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 disklabel
will not install bootstrap code that overlaps it.
.Sh NOTES
On i386 machines,
.Xr installboot 8
is normally used to install boot code.  The
.Fl B
option to
.Nm disklabel
can still be used to install old style boot code,
but this usage is deprecated.
.Sh 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 others.  In
.Fl E
mode,
.Nm 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
.Fl E
mode, partitions outside the OpenBSD portion of the disk should
be changable.