| GPT(8) | System Manager's Manual | GPT(8) |
gpt — GUID
partition table maintenance utility
gpt |
[general_options] command [command_options] device ... |
The gpt utility provides the necessary
functionality to manipulate GUID partition tables (GPTs), but see
BUGS below for how and where functionality is
missing. The basic usage model of the gpt tool
follows that of the 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 device is either a special file corresponding to a
disk-like device or a regular file. The command is applied to each
device listed on the command line.
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.
The -f option causes the
gpt utility to open the device with O_SHLOCK|O_RDWR
mode. Use this mode cautiously. It may conflict with other tasks currently
have the write access to the same device.
The -p count option
allows the user to change the number of partitions the GPT can accommodate.
This is used whenever a new GPT is created. By default, the
gpt utility will create space for 128 partitions (or
32 sectors of 512 bytes).
The -r option causes the
gpt utility to open the device for reading only.
Currently this option is primarily useful for the
show command, but the intent is to use it to
implement dry-run behaviour.
The -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.
gpt add
[-b number]
[-i index]
[-s count]
[-t type]
device ...add command allows the user to add a new
partition to an existing table. By default, it will create an HFS
partition covering the first available block of an unused disk space. The
command-specific options can be used to control this behaviour.
The -b 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.
The -i 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.
The -s count
option allows the user to specify the size of the partition in sectors.
The minimum size is 1.
The -t type
option allows the user to specify the partition type. The type is given
as an UUID, but gpt accepts
efi, hfs,
apfs, linux and
windows as aliases for the most commonly used
partition types.
gpt create
[-fp] device ...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 -f
option. If the -f option is specified, an existing
MBR is destroyed and any partitions described by the MBR are lost.
The -p option tells
gpt to create only the primary table and not the
backup table. This option is only useful for debugging and should not be
used otherwise.
gpt destroy
[-r] device ...destroy command allows the user to destroy an
existing, possibly not empty GPT.
The -r option instructs
gpt to destroy the table in a way that it can be
recovered.
gpt label
[-a] ⟨-f
file | -l
label⟩ device ...gpt label
[-b number]
[-i index]
[-s count]
[-t type]
⟨-f file |
-l label⟩
device ...label command allows the user to label any
partitions that match the selection. At least one of the following
selection options must be specified.
The -a option specifies that all
partitions should be labeled. It is mutually exclusive with all other
selection options.
The -b number
option selects the partition that starts at the given block number.
The -i index
option selects the partition with the given partition number.
The -s count
option selects all partitions that have the given size. This can cause
multiple partitions to be removed.
The -t type
option selects all partitions that have the given type. The type is
given as an UUID or by the aliases that the add
command accepts. This can cause multiple partitions to be removed.
The -f file or
-l label options specify
the new label to be assigned to the selected partitions. The
-f 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 (-), the label is
read from the standard input. The -l
label option is used to specify the label in the
command line. The label is assumed to be encoded in UTF-8.
gpt recover
device ...recover command allows the user to recover the
GPT from the backup table.gpt remove
[-a] device ...gpt remove
[-b number]
[-i index]
[-s count]
[-t type]
device ...remove command allows the user to remove any
and all partitions that match the selection. It uses the same selection
options as the label command. See above for a
description of these options. Partitions are removed by clearing the
partition type. No other information is changed.gpt show
[-l] device ...show command displays the current partitioning
on the listed devices and gives an overall view of the disk contents. With
the -l option the GPT partition label will be
displayed instead of the GPT partition type. The option has no effect on
non-GPT partitions.The gpt utility appeared in
FreeBSD 5.0 for ia64.
The development of the gpt 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.
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 -p
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.
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.
| May 7, 2012 | Mac OS X 12 |