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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 ei-
     ther 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 -p 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 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 ev-
     ery 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 ex-
	     isting table.  By default,	it will	create a UFS partition cover-
	     ing the first available block of an unused	disk space.  The com-
	     mand-specific options can be used to control this behaviour.

	     The -b number option allows the user to specify the starting (be-
	     ginning) sector number of the partition.  The minimum sector num-
	     ber 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 de-
	     fault, 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 boot, efi, swap,
	     ufs, zfs, hfs, linux and windows as aliases for the most commonly
	     used partition types.

     gpt boot [-b pmbr]	[-g gptboot] [-s count]	device ...
	     The boot command allows the user to make a	GPT labeled disk
	     bootable via the BIOS bootstrap on	i386 and amd64 machines.  By
	     default, the /boot/pmbr boot loader is installed into the PMBR
	     and the /boot/gptboot boot	loader is installed into the first
	     boot partition.  If no boot partition exists and there is avail-
	     able space, a boot	partition will be created.

	     The -b pmbr option	allows the user	to specify an alternate	path
	     for the PMBR boot loader.

	     The -g gptboot option allows the user to specify an alternate
	     path for the GPT boot loader that is installed into the boot par-
	     tition.

	     The -s count option allows	the user to specify the	size in	sec-
	     tors 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.

     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 op-
	     tions 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 as-
	     signed 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 as-
	     sumed to be encoded in UTF-8.

     gpt migrate [-fs] device ...
	     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 op-
	     tion will cause unknown partitions	to be ignored and any data in
	     it	to be lost.

	     The -s option prevents migrating BSD disk labels into GPT parti-
	     tions by creating the GPT equivalent of a slice.

     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 op-
	     tions 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 [-lu] 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.  With the	-u option the GPT partition type is displayed
	     as	an UUID	instead	of in a	user friendly form.  The -l option
	     takes precedence over the -u option.

SEE ALSO
     fdisk(8), mount(8), newfs(8), swapon(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 di-
     agnostic 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			       February	5, 2008				   BSD

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | HISTORY | BUGS

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