path: root/sbin/gpt/gpt.8

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.Dd October 24, 2007
.Os
.Dt GPT 8
.Sh NAME
.Nm gpt
.Nd "GUID partition table maintenance utility"
.Sh SYNOPSIS
.Nm
.Op Ar general_options
.Ar command
.Op Ar command_options
.Ar device ...
.Sh DESCRIPTION
The
.Nm
utility provides the necessary functionality to manipulate GUID partition
tables (GPTs), but see
.Sx BUGS
below for how and where functionality is missing.
The basic usage model of the
.Nm
tool follows that of the
.Xr cvs 1
tool.
The general options are described in the following paragraph.
The remaining paragraphs describe the individual commands with their options.
Here we conclude by mentioning that a
.Ar device
is either a special file
corresponding to a disk-like device or a regular file.
The command is applied to each
.Ar device
listed on the command line.
.Ss General Options
The general options allow the user to change default settings or otherwise
change the behaviour that is applicable to all commands.
Not all commands use all default settings, so some general options may not
have an effect on all commands.
.Pp
The
.Fl p Ar count
option allows the user to change the number of partitions the GPT can
accomodate.
This is used whenever a new GPT is created.
By default, the
.Nm
utility will create space for 128 partitions (or 32 sectors of 512 bytes).
.Pp
The
.Fl r
option causes the
.Nm
utility to open the device for reading only.
Currently this option is primarily useful for the
.Ic show
command, but the intent
is to use it to implement dry-run behaviour.
.Pp
The
.Fl v
option controls the verbosity level.
The level increases with every occurrence of this option.
There is no formalized definition of the different levels yet.
.Ss Commands
.Bl -tag -width indent
.\" ==== add ====
.It Xo
.Nm
.Ic add
.Op Fl b Ar number
.Op Fl i Ar index
.Op Fl s Ar count
.Op Fl t Ar type
.Ar device ...
.Xc
The
.Ic add
command allows the user to add a new partition to an existing table.
By default, it will create a UFS partition covering the first available block
of an unused disk space.
The command-specific options can be used to control this behaviour.
.Pp
The
.Fl b Ar number
option allows the user to specify the starting (beginning) sector number of
the partition.
The minimum sector number is 1, but has to fall inside an unused region of
disk space that is covered by the GPT.
.Pp
The
.Fl i Ar index
option allows the user to specify which (free) entry in the GPT table is to
be used for the new partition.
By default, the first free entry is selected.
.Pp
The
.Fl s Ar count
option allows the user to specify the size of the partition in sectors.
The minimum size is 1.
.Pp
The
.Fl t Ar type
option allows the user to specify the partition type.
The type is given as an UUID, but
.Nm
accepts
.Cm boot , efi , swap , ufs , zfs, hfs , linux
and
.Cm windows
as aliases for the most commonly used partition types.
.\" ==== boot ====
.It Xo
.Nm
.Ic boot
.Op Fl b Ar pmbr
.Op Fl g Ar gptboot
.Op Fl s Ar count
.Ar device ...
.Xc
The
.Ic boot
command allows the user to make a GPT labeled disk bootable via the BIOS
bootstrap on i386 and amd64 machines.
By default,
the
.Pa /boot/pmbr
boot loader is installed into the PMBR and the
.Pa /boot/gptboot
boot loader is installed into the first boot partition.
If no boot partition exists and there is available space,
a boot partition will be created.
.Pp
The
.Fl b Ar pmbr
option allows the user to specify an alternate path for the PMBR boot loader.
.Pp
The
.Fl g Ar gptboot
option allows the user to specify an alternate path for the GPT boot loader
that is installed into the boot partition.
.Pp
The
.Fl s Ar count
option allows the user to specify the size in sectors of the boot partition
if one does not already exist.
A boot partition must be at least 16 kilobytes.
By default,
a size of 64 kilobytes is used.
Note that the PMBR boot loader will load the entire boot partition into
memory.
As a result, the boot partition may not exceed 545 kilobytes.
.\" ==== create ====
.It Nm Ic create Oo Fl fp Oc Ar device ...
The
.Ic create
command allows the user to create a new (empty) GPT.
By default, one cannot create a GPT when the device contains a MBR,
however this can be overridden with the
.Fl f
option.
If the
.Fl f
option is specified, an existing MBR is destroyed and any partitions
described by the MBR are lost.
.Pp
The
.Fl p
option tells
.Nm
to create only the primary table and not the backup table.
This option is only useful for debugging and should not be used otherwise.
.\" ==== destroy ====
.It Nm Ic destroy Oo Fl r Oc Ar device ...
The
.Ic destroy
command allows the user to destroy an existing, possibly not empty GPT.
.Pp
The
.Fl r
option instructs
.Nm
to destroy the table in a way that it can be recovered.
.\" ==== label ====
.It Xo
.Nm
.Ic label
.Op Fl a
.Aq Fl f Ar file | Fl l Ar label
.Ar device ...
.Xc
.It Xo
.Nm
.Ic label
.Op Fl b Ar number
.Op Fl i Ar index
.Op Fl s Ar count
.Op Fl t Ar type
.Aq Fl f Ar file | Fl l Ar label
.Ar device ...
.Xc
The
.Ic label
command allows the user to label any partitions that match the selection.
At least one of the following selection options must be specified.
.Pp
The
.Fl a
option specifies that all partitions should be labeled.
It is mutually exclusive with all other selection options.
.Pp
The
.Fl b Ar number
option selects the partition that starts at the given block number.
.Pp
The
.Fl i Ar index
option selects the partition with the given partition number.
.Pp
The
.Fl s Ar count
option selects all partitions that have the given size.
This can cause multiple partitions to be removed.
.Pp
The
.Fl t Ar type
option selects all partitions that have the given type.
The type is given as an UUID or by the aliases that the
.Ic add
command accepts.
This can cause multiple partitions to be removed.
.Pp
The
.Fl f Ar file
or
.Fl l Ar label
options specify the new label to be assigned to the selected partitions.
The
.Fl f Ar file
option is used to read the label from the specified file.
Only the first line is read from the file and the trailing newline
character is stripped.
If the file name is the dash or minus sign
.Pq Fl ,
the label is read from
the standard input.
The
.Fl l Ar label
option is used to specify the label in the command line.
The label is assumed to be encoded in UTF-8.
.\" ==== migrate ====
.It Nm Ic migrate Oo Fl fs Oc Ar device ...
The
.Ic migrate
command allows the user to migrate an MBR-based disk partitioning into a
GPT-based partitioning.
By default, the MBR is not migrated when it contains partitions of an unknown
type.
This can be overridden with the
.Fl f
option.
Specifying the
.Fl f
option will cause unknown partitions to be ignored and any data in it
to be lost.
.Pp
The
.Fl s
option prevents migrating
.Bx
disk labels into GPT partitions by creating
the GPT equivalent of a slice.
.\" ==== remove ====
.It Nm Ic remove Oo Fl a Oc Ar device ...
.It Xo
.Nm
.Ic remove
.Op Fl b Ar number
.Op Fl i Ar index
.Op Fl s Ar count
.Op Fl t Ar type
.Ar device ...
.Xc
The
.Ic remove
command allows the user to remove any and all partitions that match the
selection.
It uses the same selection options as the
.Ic label
command.
See above for a description of these options.
Partitions are removed by clearing the partition type.
No other information is changed.
.\" ==== show ====
.It Nm Ic show Oo Fl lu Oc Ar device ...
The
.Ic show
command displays the current partitioning on the listed devices and gives
an overall view of the disk contents.
With the
.Fl l
option the GPT partition label will be displayed instead of the GPT partition
type.
The option has no effect on non-GPT partitions.
With the
.Fl u
option the GPT partition type is displayed as an UUID instead of in a
user friendly form.
The
.Fl l
option takes precedence over the
.Fl u
option.
.El
.Sh SEE ALSO
.Xr fdisk 8 ,
.Xr mount 8 ,
.Xr newfs 8 ,
.Xr swapon 8
.Sh HISTORY
The
.Nm
utility appeared in
.Fx 5.0
for ia64.
.Sh BUGS
The development of the
.Nm
utility is still work in progress.
Many necessary features are missing or partially implemented.
In practice this means that the manual page, supposed to describe these
features, is farther removed from being complete or useful.
As such, missing functionality is not even documented as missing.
However, it is believed that the currently present functionality is reliable
and stable enough that this tool can be used without bullet-proof footware if
one thinks one does not make mistakes.
.Pp
It is expected that the basic usage model does not change, but it is
possible that future versions will not be compatible in the strictest sense
of the word.
For example, the
.Fl p Ar count
option may be changed to a command option rather than a generic option.
There are only two commands that use it so there is a chance that the natural
tendency for people is to use it as a command option.
Also, options primarily intended for diagnostic or debug purposes may be
removed in future versions.
.Pp
Another possibility is that the current usage model is accompanied by
other interfaces to make the tool usable as a back-end.
This all depends on demand and thus feedback.