| GPT(8) | System Manager's Manual | GPT(8) | 
gpt —
| gpt | [ -Hnqrv] [-mmediasize] [-ssectorsize] [-Ttimestamp] command
      [command_options] device | 
| gpt | set -l | 
| gpt | unset -l | 
| gpt | type -l | 
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.
-H-m
    mediasize-ngpt
      changed. You need to use the
      dkctl(8) command manually
      update the device's wedge configuration if you do that.-q-rgpt Currently
      this option is primarily useful for the show
      command, but the intent is to use it to implement dry-run behaviour.-s
    sectorsize512 for plain files.-T
    timestamp-vgpt add
    [-a alignment]
    [-b blocknr]
    [-i index]
    [-l label]
    [-s size]
    [-t type]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 (case insensitive)
        are ‘b’ to denote bytes, ‘k’ to denote
        kilobytes, ‘m’ to denote megabytes and ‘g’
        to denote gigabytes, ‘t’ to denote terabytes,
        ‘p’ to denote petabytes, and ‘e’ to denote
        exabytes. 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
appleapple-ufsbiosefifbsd-legacyfbsd-swapfbsd-ufsfbsd-vinumzfslinux-datalinux-raidlinux-swaplinux-lvmwindowswindows-reservedccdcgdffslfsraidswapgpt backup
    [-o outfile]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] [-b
    startsec] [-i
    index] [-L
    label]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. This should not normally be necessary, but some firmware might
        require it. If -A is omitted, the active flag
        will be cleared from the PMBR label.
The -c option allows the user to
        specify the filename from which gpt should read
        the bootcode. The default is to read from
        /usr/mdec/gptmbr.bin.
The partition that should contain the primary bootstrap code,
        (similar to that installed via
        installboot(8)) is
        selected using the -i,
        -L and -b options. One
        of these three options is required. The -i
        option selects the partition given by the index.
        The -L option selects the partition by
        label. If there are multiple partitions with the
        same label, the first one found will be used. The
        -b option selects the partition starting at
        block startsec.
gpt create
    [-AfP] [-p
    partitions]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]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 headerheader 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⟩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]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 recoverrecover 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]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]
    [-b startsec]
    [-a alignment]
    [-s size]
    [-q]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. If the
      -q option is specified then the utility will not
      print output when a resize is not required.gpt resizedisk
    [-s size]
    [-q]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. If the -q option is specified then
        the utility will not print output when a resize is not required.
gpt restore
    [-F] [-i
    infile]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]
    [-N] [-i
    index] [-b
    startsec]gpt set
    -lset 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.
      If the -N option and no -a
      option are specified, all attributes are removed. The
      -i or the -b option
      specify 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] [-b
    startsec]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 or the -b 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
    newtypegpt type
    [-b blocknr]
    [-i index]
    [-L label]
    [-s sectors]
    [-t type]
    -T newtypegpt type
    -ltype 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]
    [-b startsec]gpt unset
    -lunset 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. Alternatively a
      comma separated list of attributes can be used. The
      -i or the -b 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.gpt uuid
    [-a]gpt uuid
    [-b blocknr]
    [-i index]
    [-L label]
    [-s sectors]
    [-t type]uuid command allows the user to change the
      UUID 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. If -a is used,
      then the header UUID is changed as well.
    The primary purpose of this command is for use after cloning a disk to prevent collisions when both disks are used in the same system.
gpt command exits with a failure status (1) when the
  header command is used and no GPT header is found. This can be used to check
  for the existence of a GPT in shell scripts.
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#
Booting from GPT on a BIOS system: this creates a bootable partition.
xotica# gpt create wd1 xotica# gpt add -b 1024 -l bootroot -t ffs -s 1g wd1 /dev/rwd1: Partition 1 added: 49f48d5a-b10e-11dc-b99b-0019d1879648 1024 2097152 xotica ~# dmesg | tail -2 wd1: GPT GUID: 660e0630-0a3f-47c0-bc52-c88bcec79392 dk0 at wd1: "bootroot", 2097152 blocks at 1024, type: ffs xotica# gpt biosboot -L bootroot wd1 xotica# newfs dk0 xotica# installboot /dev/rdk0 /usr/mdec/bootxx_ffsv1 xotica# mount /dev/dk0 /mnt xotica# cp /usr/mdec/boot /mnt
Note that biosboot is not needed for UEFI
    systems.
gpt utility appeared in FreeBSD
  5.0 for ia64. gpt utility first appeared in
  NetBSD 5.0.
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.
| April 7, 2022 | NetBSD 10.1 |