GPT(8)                    BSD System Manager's Manual                   GPT(8)

NAME
     gpt -- GUID partition table maintenance utility

SYNOPSIS
     gpt [general_options] 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 functional-
     ity 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 other-
     wise 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 sec-
     tors 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.

   Commands
     gpt add [-b number] [-i index] [-s count] [-t type] device ...
             The add command allows the user to add a new partition to an
             existing table.  By default, it will create an HFS partition cov-
             ering 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 ...
             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 par-
             titions 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 ...
             The destroy command allows the user to destroy an existing, pos-
             sibly 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 ...
             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 number option selects the partition that starts at the
             given block number.

             The -i index option selects the partition with the given parti-
             tion 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 ...
             The 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 ...
             The remove command allows the user to remove any and all parti-
             tions 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 ...
             The 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 par-
             titions.

SEE ALSO
     fdisk(8), mount(8), newfs(8), pdisk(8)

HISTORY
     The gpt utility appeared in FreeBSD 5.0 for ia64.

BUGS
     The development of the gpt utility is still work in progress.  Many nec-
     essary features are missing or partially implemented.  In practice this
     means that the manual page, supposed to describe these features, is far-
     ther removed from being complete or useful.  As such, missing functional-
     ity 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 pos-
     sible 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 com-
     mand 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.

BSD                               May 7, 2012                              BSD