1 .\" Copyright (c) 2002 Marcel Moolenaar
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25 .\" $FreeBSD: src/sbin/gpt/gpt.8,v 1.17 2006/06/22 22:22:32 marcel Exp $
26 .\" $DragonFly: src/sbin/gpt/gpt.8,v 1.4.4.1 2008/08/04 20:41:13 thomas Exp $
33 .Nd "GUID partition table maintenance utility"
36 .Op Ar general_options
38 .Op Ar command_options
43 utility provides the necessary functionality to manipulate GUID partition
44 tables (GPTs), but see
46 below for how and where functionality is missing.
47 GPT partitions are accessed as
49 disk slices, with same number as GPT partition.
50 The basic usage model of the
52 tool follows that of the
55 The general options are described in the following paragraph.
56 The remaining paragraphs describe the individual commands with their options.
57 Here we conclude by mentioning that a
59 is either a special file
60 corresponding to a disk-like device or a regular file.
61 The command is applied to each
63 listed on the command line.
65 The general options allow the user to change default settings or otherwise
66 change the behaviour that is applicable to all commands.
67 Not all commands use all default settings, so some general options may not
68 have an effect on all commands.
72 option allows the user to change the number of partitions the GPT can
74 This is used whenever a new GPT is created.
77 utility will create space for 128 partitions (or 32 sectors of 512 bytes).
83 utility to open the device for reading only.
84 Currently this option is primarily useful for the
86 command, but the intent
87 is to use it to implement dry-run behaviour.
91 option controls the verbosity level.
92 The level increases with every occurrence of this option.
93 There is no formalized definition of the different levels yet.
95 .Bl -tag -width indent
108 command allows the user to add a new partition to an existing table,
109 the name of the disk slice for the added partition is printed.
110 By default, it will create a
112 partition covering the first available block
113 of an unused disk space.
114 The command-specific options can be used to control this behaviour.
118 option allows the user to specify the starting (beginning) sector number of
120 The minimum sector number is 1, but has to fall inside an unused region of
121 disk space that is covered by the GPT.
125 option allows the user to specify which (free) entry in the GPT table is to
126 be used for the new partition.
127 By default, the first free entry is selected.
128 Entries start at index 0 representing partition 0 of the GPT.
132 option allows the user to specify the size of the partition in sectors.
133 The minimum size is 1.
137 option allows the user to specify the partition type.
138 The type is given as an UUID, but
141 .Cm efi , swap , ufs , hfs , linux , dfly ,
144 as aliases for the most commonly used partition types.
156 You may also specify any symbolic name in the system
160 .It Nm Ic create Oo Fl fp Oc Ar device ...
163 command allows the user to create a new (empty) GPT.
164 By default, one cannot create a GPT when the device contains a MBR,
165 however this can be overridden with the
170 option is specified, an existing MBR is destroyed and any partitions
171 described by the MBR are lost.
177 to create only the primary table and not the backup table.
178 This option is only useful for debugging and should not be used otherwise.
179 .\" ==== destroy ====
180 .It Nm Ic destroy Oo Fl r Oc Ar device ...
183 command allows the user to destroy an existing, possibly not empty GPT.
189 to destroy the table in a way that it can be recovered.
195 .Aq Fl f Ar file | Fl l Ar label
205 .Aq Fl f Ar file | Fl l Ar label
210 command allows the user to label any partitions that match the selection.
211 At least one of the following selection options must be specified.
215 option specifies that all partitions should be labeled.
216 It is mutually exclusive with all other selection options.
220 option selects the partition that starts at the given block number.
224 option selects the partition with the given partition number.
225 Partition numbers start at 0.
229 option selects all partitions that have the given size.
230 This can cause multiple partitions to be removed.
234 option selects all partitions that have the given type.
235 The type is given as an UUID or by the aliases that the
238 This can cause multiple partitions to be removed.
244 options specify the new label to be assigned to the selected partitions.
247 option is used to read the label from the specified file.
248 Only the first line is read from the file and the trailing newline
249 character is stripped.
250 If the file name is the dash or minus sign
252 the label is read from
256 option is used to specify the label in the command line.
257 The label is assumed to be encoded in UTF-8.
258 .\" ==== migrate ====
259 .It Nm Ic migrate Oo Fl fs Oc Ar device ...
262 command allows the user to migrate an MBR-based disk partitioning into a
263 GPT-based partitioning.
264 By default, the MBR is not migrated when it contains partitions of an unknown
266 This can be overridden with the
271 option will cause unknown partitions to be ignored and any data in it
276 option prevents migrating
278 disk labels into GPT partitions by creating
279 the GPT equivalent of a slice.
281 .It Nm Ic remove Oo Fl a Oc Ar device ...
293 command allows the user to remove any and all partitions that match the
295 It uses the same selection options as the
298 See above for a description of these options.
299 Partitions are removed by clearing the partition type.
300 No other information is changed.
302 .It Nm Ic show Oo Fl lu Oc Ar device ...
305 command displays the current partitioning on the listed devices and gives
306 an overall view of the disk contents.
309 option the GPT partition label will be displayed instead of the GPT partition
311 The option has no effect on non-GPT partitions.
314 option the GPT partition type is displayed as an UUID instead of in a
318 option takes precedence over the
323 .Bl -tag -width ".Pa /etc/defaults/uuids"
324 .It Pa /etc/defaults/uuids
326 and their symbolic names provided by the OS vendor.
329 and their symbolic names provided by the system administrator.
332 To install an empty GPT on
337 GPT partitions are defined in number of sectors, the sector size is usually 512B,
338 which is assumed in the examples below, it can be found using:
340 .Dl "gpt -v show ad6"
342 To add a dummy GPT partition 0:
344 .Dl "gpt add -i0 -s1 ad6"
346 You might want to do this to not use slice 0 for data;
347 when GPT is not used on a disk, slice 0 is the compatibility slice,
349 .Dq dangerously dedicated
351 For GPT slice 0 has no special meaning, it is just the first slice on the disk.
353 To add a GPT partition of size approx. 100GB:
355 .Dl "gpt add -s200000000 ad6"
357 This will be GPT partition 1 as it is the first one free,
358 it will be accessible as
360 which is also printed by the command.
362 .Dq DragonFly Label64 ,
363 it will have to be set up by
366 To add GPT partition 5 with type
368 using the remaining free space:
369 .Bd -literal -offset indent
370 gpt add -i5 -t "DragonFly HAMMER" ad6
373 To print the contents of the GPT:
379 manipulates is part of the EFI standard and is supported by many OSs.
380 GPT uses 64 bits to store number of sectors, this supports very large disks.
381 With the prevalent sector size of 512B this is 8 billion TB.
402 The development of the
404 utility is still work in progress.
405 Many necessary features are missing or partially implemented.
406 In practice this means that the manual page, supposed to describe these
407 features, is farther removed from being complete or useful.
408 As such, missing functionality is not even documented as missing.
409 However, it is believed that the currently present functionality is reliable
410 and stable enough that this tool can be used without bullet-proof footware if
411 one thinks one does not make mistakes.
413 It is expected that the basic usage model does not change, but it is
414 possible that future versions will not be compatible in the strictest sense
418 option may be changed to a command option rather than a generic option.
419 There are only two commands that use it so there is a chance that the natural
420 tendency for people is to use it as a command option.
421 Also, options primarily intended for diagnostic or debug purposes may be
422 removed in future versions.
424 Another possibility is that the current usage model is accompanied by
425 other interfaces to make the tool usable as a back-end.
426 This all depends on demand and thus feedback.
430 command doesn't support
435 doesn't support booting from GPT partitions.