NAME
gpt —
GUID partition table maintenance
utility
SYNOPSIS
gpt |
[-nrqv]
[-m
mediasize]
[-s
sectorsize]
[-T
timestamp] command
[command_options]
device |
DESCRIPTION
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.
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.
-
-
- -m
mediasize
- Override the default media size for the device (obtained
from the kernel if possible) or defaulting to the file size for plain
files.
-
-
- -n
- Do not update the wedge information that
gpt changed. You need to use the
dkctl(8) command manually
update the device's wedge configuration if you do that.
-
-
- -r
- Open the device for reading only. gpt
Currently this option is primarily useful for the show
command, but the intent is to use it to implement dry-run behaviour.
-
-
- -q
- Do not print error messages. This is not implemented
completely yet.
-
-
- -s
sectorsize
- Override the default sector size for the device (obtained
from the kernel if possible) or
512
for plain
files.
-
-
- -T
timestamp
- Specify a timestamp to be used for uuid generation so that
uuids are not random and can be consistent for reproducible builds. The
timestamp can be a pathname, where the timestamps are derived from that
file, a parseable date for parsedate(3) (this option is not yet available
in the tools build), or an integer value interpreted as the number of
seconds from the Epoch.
-
-
- -v
- Controls the verbosity level. The level increases with
every occurrence of this option. There is no formalized definition of the
different levels yet.
Commands
-
-
- gpt
add [-a
alignment]
[-b blocknr]
[-i index]
[-l label]
[-s size]
[-t
type]
- The 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.
The -a alignment option allows the
user to specify an alignment for the start and size. The alignment is
given in bytes and may have a suffix to indicate its magnitude.
gpt will attempt to align the partition.
The -b blocknr 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 -l label option allows the user
to specify a label for the partition.
The -s size option allows the user
to specify the size of the partition. If there is no suffix, or the suffix
is ‘s’ or ‘S’ then size is in sectors, otherwise
size is in bytes which must be a multiple of the device's sector size.
Accepted suffix units are ‘b’ to denote bytes, ‘k’
to denote kilobytes, ‘m’ to denote megabytes and
‘g’ to denote gigabytes. The minimum size is 1 sector.
The -t type option allows the user
to specify the partition type. The type is given as an UUID, but
gpt accepts
- apple
- Apple HFS
- apple-ufs
- Apple UFS
- bios
- BIOS Boot
- efi
- EFI System
- fbsd-legacy
- FreeBSD legacy
- fbsd-swap
- FreeBSD swap
- fbsd-ufs
- FreeBSD UFS/UFS2
- fbsd-vinum
- FreeBSD vinum
- fbsd-zfs
- FreeBSD ZFS
- linux-data
- Linux data
- linux-raid
- Linux RAID
- linux-swap
- Linux swap
- linux-lvm
- Linux LVM
- windows
- Windows basic data
- windows-reserved
- Windows reserved
- ccd
- NetBSD ccd component
- cgd
- NetBSD Cryptographic Disk
- ffs
- NetBSD FFSv1/FFSv2
- lfs
- NetBSD LFS
- raid
- NetBSD RAIDFrame component
- swap
- NetBSD swap
as aliases for the most commonly used partition types.
-
-
- gpt
backup [-o
outfile]
- The backup command dumps the MBR or
(PMBR) and GPT partition tables to standard output or to a file specified
by the outfile argument in a format to be used by
the restore command. The format is a plist. It should
not be modified.
-
-
- gpt
biosboot [-A]
[-c
bootcode]
[-i index]
[-L
label]
- The biosboot command allows the user to
configure the partition that contains the primary bootstrap program, used
during boot(8).
The -A options sets the PMBR partition active.
The -c option allows the user to specify the filename that
gpt should read the bootcode from. The default is to
read from /usr/mdec/gptmbr.bin.
The -i option selects the partition that should contain
the primary bootstrap code, as installed via
installboot(8). The
-L option selects the partition by label. If there are
multiple partitions with the same label, the first one found will be
used.
-
-
- gpt
create [-AfP]
[-p
partitions]
- The 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 -A options sets the PMBR partition active.
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.
The -p option changes the default 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).
-
-
- gpt
destroy
[-r]
- The 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
header
- The header command displays size
information about the media and information from the GPT header if it
exists.
-
-
- gpt
label [-a]
⟨-f file |
-l label⟩
-
- gpt
label [-b
blocknr] [-i
index] [-L
label] [-s
sectors] [-t
type] ⟨-f
file | -l
label⟩
- The 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 blocknr option selects the
partition that starts at the given block number.
The -i index option selects the
partition with the given partition number.
The -L label option selects all
partitions that have the given label. This can cause multiple partitions
to be relabeled.
The -s sectors option selects all
partitions that have the given size. This can cause multiple partitions to
be labeled.
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 labeled.
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
migrate [-Afs]
[-p
partitions]
- The 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 -f option.
Specifying the -f option will cause unknown partitions
to be ignored and any data in it to be lost.
The -A options sets the PMBR partition active.
The -s option prevents migrating
BSD disk labels into GPT partitions by creating
the GPT equivalent of a slice. Note that the -s option
is not applicable to NetBSD partitions.
The -p option changes the default 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 migrate command requires space at the beginning and
the end of the device outside any partitions to store the GPTs. Space is
required for the GPT header (which takes one sector) and the GPT partition
table. See the -p option for the size of the GPT
partition table. By default, just about all devices have a minimum of 62
sectors free at the beginning of the device, but do not have any free
space at the end. For the default GPT partition table size on a 512 byte
sector size device, 33 sectors at the end of the device would need to be
freed.
-
-
- gpt
recover
- The recover command tries to restore the
GPT partition label from the backup near the end of the disk. It is very
useful in case the primary label was deleted.
-
-
- gpt
remove [-a]
-
- gpt
remove [-b
blocknr] [-i
index] [-L
label] [-s
sectors] [-t
type]
- The 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
resize -i index
[-a
alignment]
[-s
size]
- The resize command allows the user to
resize a partition. The partition may be shrunk and if there is sufficient
free space immediately after it then it may be expanded. The
-s option allows the new size to be specified, otherwise
the partition will be increased to the maximum available size. If there is
no suffix, or the suffix is ‘s’ or ‘S’ then size
is in sectors, otherwise size is in bytes which must be a multiple of the
device's sector size. Accepted suffix units are ‘b’ to denote
bytes, ‘k’ to denote kilobytes, ‘m’ to denote
megabytes and ‘g’ to denote gigabytes. The minimum size is 1
sector. If the -a option is specified then the size will
be adjusted to be a multiple of alignment if possible.
-
-
- gpt
resizedisk [-s
size]
- The resizedisk command allows the user to
resize a disk. With GPTs, a backup copy is stored at the end of the disk.
If the underlying medium changes size (or is going to change size), then
the backup copy needs to be moved to the new end of the disk, and the last
sector available for data storage needs to be adjusted. This command does
that. If the backup copy no longer exists due to the medium shrinking,
then a new backup copy will be created using the primary copy.
The -s option allows the new size to be specified,
otherwise the backup copy will automatically be placed at the current end
of the disk. If there is no suffix, or the suffix is ‘s’ or
‘S’ then size is in sectors, otherwise size is in bytes which
must be a multiple of the device's sector size. Accepted suffix units are
‘b’ to denote bytes, ‘k’ to denote kilobytes,
‘m’ to denote megabytes and ‘g’ to denote
gigabytes. Using the -s option allows you to move the
backup copy prior to resizing the medium. This is primarily useful when
shrinking the medium.
-
-
- gpt
restore [-F]
[-i
infile]
- The restore command restores a partition
table that was previously saved using the backup
command. The partition table is read from standard input or a file
specified in the infile argument and is expected to
be in the format of a plist. It assumes an empty disk. The
-F option can be used to blank the disk. The new disk
does not have to be the same size as the old disk as long as all the
partitions fit, as restore will automatically adjust.
However, the new disk must use the same sector size as the old disk.
-
-
- gpt
set -a attribute
-i index
-
- gpt
set -l
- The set command sets various partition
attributes. The -l flag lists all available attributes.
The -a option specifies which attributes to set and may
be specified more than once, or the attributes can be comma-separated. The
-i option specifies which entry to update. The possible
attributes are “biosboot”, “bootme”,
“bootonce”, “bootfailed”, “noblockio”,
and “required”. The biosboot flag is used to indicate which
partition should be booted by legacy BIOS boot code. See the
biosboot command for more information. The bootme flag
is used to indicate which partition should be booted by UEFI boot code.
The other attributes are for compatibility with
FreeBSD and are not currently used by
NetBSD. They may be used by
NetBSD in the future.
-
-
- gpt
show [-aglu]
[-i
index]
- The show command displays the current
partitioning on the listed devices and gives an overall view of the disk
contents. With the -g option the GPT partition GUID will
be displayed instead of the GPT partition type. With the
-l option the GPT partition label will be displayed
instead of the GPT partition type. With the -u option
the GPT partition type is displayed as an UUID instead of in a user
friendly form. With the -i option, all the details of a
particular GPT partition will be displayed. The format of this display is
subject to change. With the -a option, all information
for all GPT partitions (just like with -i
index) will be printed. None of the options have any
effect on non-GPT partitions. The order of precedence for the options are:
-a, -i, -l,
-g, -u.
-
-
- gpt
type [-a]
-T newtype
-
- gpt
type [-b
blocknr] [-i
index] [-L
label] [-s
sectors] [-t
type] -T
newtype
-
- gpt
type -l
- The type command allows the user to
change the type of 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. The -l
flag lists available types.
-
-
- gpt
unset -a attribute
-i index
-
- gpt
unset -l
- The unset command unsets various
partition attributes. The -l flag lists all available
attributes. The -a option specifies which attributes to
unset and may be specified more than once. The -i option
specifies which entry to update. The possible attributes are
“biosboot”, “bootme”, “bootonce”,
“bootfailed”, “noblockio”, and
“required”. The biosboot flag is used to indicate which
partition should be booted by legacy BIOS boot code. See the
biosboot command for more information. The other
attributes are for compatibility with FreeBSD and
are not currently used by any NetBSD code. They
may be used by NetBSD code in the future.
EXAMPLES
nas# gpt show wd3
start size index contents
0 1 PMBR
1 3907029167
nas# gpt create wd3
nas# gpt show wd3
start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 3907029101
3907029135 32 Sec GPT table
3907029167 1 Sec GPT header
nas# gpt add -s 10486224 -t swap -i 1 wd3
nas# gpt label -i 1 -l swap_1 wd3
partition 1 on rwd3d labeled swap_1
nas# gpt show wd3
start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 10486224 1 GPT part - NetBSD swap
10486258 3896542877
3907029135 32 Sec GPT table
3907029167 1 Sec GPT header
nas# gpt show -l wd3
start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 10486224 1 GPT part - "swap_1"
10486258 3896542877
3907029135 32 Sec GPT table
3907029167 1 Sec GPT header
nas#
SEE ALSO
boot(8),
dkctl(8),
fdisk(8),
installboot(8),
mount(8),
newfs(8),
swapon(8)
HISTORY
The
gpt utility appeared in
FreeBSD
5.0 for ia64.
gpt utility first appeared in
NetBSD 5.0.
BUGS
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. 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.