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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 .\"
27 .Dd September 28, 2009
28 .Dt GPT 8
29 .Os
30 .Sh NAME
31 .Nm gpt
32 .Nd "GUID partition table maintenance utility"
33 .Sh SYNOPSIS
34 .Nm
35 .Op Ar general_options
36 .Ar command
37 .Op Ar command_options
38 .Ar device ...
39 .Sh DESCRIPTION
40 The
41 .Nm
42 utility provides the necessary functionality to manipulate GUID partition
43 tables (GPTs), but see
44 .Sx BUGS
45 below for how and where functionality is missing.
46 GPT partitions are accessed as
47 .Dx
48 disk slices, with same number as GPT partition,
49 127 slices per disk device are supported.
50 The basic usage model of the
51 .Nm
52 tool follows that of the
53 .Xr cvs 1
54 tool.
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
58 .Ar device
59 is either a special file
60 corresponding to a disk-like device or a regular file.
61 The command is applied to each
62 .Ar device
63 listed on the command line.
64 .Ss General Options
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.
69 .Pp
70 The
71 .Fl p Ar count
72 option allows the user to change the number of partitions the GPT can
73 accommodate.
74 This is used whenever a new GPT is created.
75 By default, the
76 .Nm
77 utility will create space for 128 partitions (or 32 sectors of 512 bytes).
78 .Pp
79 The
80 .Fl r
81 option causes the
82 .Nm
83 utility to open the device for reading only.
84 Currently this option is primarily useful for the
85 .Ic show
86 command, but the intent
87 is to use it to implement dry-run behaviour.
88 .Pp
89 The
90 .Fl v
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.
94 .Ss Commands
95 .Bl -tag -width indent
96 .\" ==== add ====
97 .It Xo
98 .Nm
99 .Ic add
100 .Op Fl b Ar number
101 .Op Fl i Ar index
102 .Op Fl s Ar count
103 .Op Fl t Ar type
104 .Ar device ...
105 .Xc
106 The
107 .Ic add
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
111 .Cm dfly
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.
115 .Pp
116 The
117 .Fl b Ar number
118 option allows the user to specify the starting (beginning) sector number of
119 the partition.
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.
122 .Pp
123 The
124 .Fl i Ar index
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.
129 .Pp
130 The
131 .Fl s Ar count
132 option allows the user to specify the size of the partition in sectors.
133 The minimum size is 1.
134 .Pp
135 The
136 .Fl t Ar type
137 option allows the user to specify the partition type.
138 The type is given as an UUID, but
139 .Nm
140 accepts
141 .Cm efi , swap , ufs , hfs , linux , dfly ,
142 and
143 .Cm windows
144 as aliases for the most commonly used partition types.
145 .Cm ufs
146 is a
147 .Fx
148 UFS UUID.
149 .Cm dfly
150 has the alias
151 .Cm dragonfly
152 and is a
153 .Dx
154 .Xr disklabel64 5
155 UUID.
156 You may also specify any symbolic name in the system
157 .Xr uuids 5
158 files.
159 .Pp
160 .Em NOTE!
161 If you don't specify a beginning sector with
162 .Fl b Ar number
163 , the new partition will be aligned to 1MiB in size and position
164 (in case of 512 byte sector sizes).
165 .\" ==== boot ====
166 .It Nm Ic boot Ar device ...
167 The
168 .Ic boot
169 command allows the user to create a small boot partition in a freshly
170 created GPT.
171 .Pp
172 This command creates a small, 1GB boot partition as partition #0
173 and hacks in a special
174 .Sq slice 1
175 in the PMBR which aliases it.
176 The PMBR is further modified to add the necessary boot code.
177 You can then disklabel GPT partition #0 and mount it, placing the contents of
178 .Pa /boot
179 directory within.
180 You must add a line to
181 .Pa loader.conf ,
182 like
183 .Bd -literal -offset indent
184 vfs.root.mountfrom="ufs:da1s1a"
185 .Ed
186 .Pp
187 which point to the actual root mount.
188 .Pp
189 Your root partition may be another GPT partition and you may use a 64 bit
190 disklabel within that partition if you desire.
191 .Pp
192 The
193 .Sq boot0
194 boot manager is used, it can be manipulated with the
195 .Xr boot0cfg 8
196 command,
197 .Sq packet
198 option usually needs to be set.
199 .Pp
200 .Em NOTE!
201 A disk setup with the
202 .Ar boot
203 command may not be shared with another OS,
204 as it doesn't use a fully standard GPT.
205 .Pp
206 .Em WARNING!
207 Some BIOSes may not be able to deal with this hack, your mileage may vary.
208 .\" ==== create ====
209 .It Nm Ic create Oo Fl fp Oc Ar device ...
210 The
211 .Ic create
212 command allows the user to create a new (empty) GPT.
213 By default, one cannot create a GPT when the device contains a MBR,
214 however this can be overridden with the
215 .Fl f
216 option.
217 If the
218 .Fl f
219 option is specified, an existing MBR is destroyed and any partitions
220 described by the MBR are lost.
221 .Pp
222 The
223 .Fl p
224 option tells
225 .Nm
226 to create only the primary table and not the backup table.
227 This option is only useful for debugging and should not be used otherwise.
228 .\" ==== destroy ====
229 .It Nm Ic destroy Oo Fl r Oc Ar device ...
230 The
231 .Ic destroy
232 command allows the user to destroy an existing, possibly not empty GPT.
233 .Pp
234 The
235 .Fl r
236 option instructs
237 .Nm
238 to destroy the table in a way that it can be recovered.
239 .\" ==== label ====
240 .It Xo
241 .Nm
242 .Ic label
243 .Op Fl a
244 .Aq Fl f Ar file | Fl l Ar label
245 .Ar device ...
246 .Xc
247 .It Xo
248 .Nm
249 .Ic label
250 .Op Fl b Ar number
251 .Op Fl i Ar index
252 .Op Fl s Ar count
253 .Op Fl t Ar type
254 .Aq Fl f Ar file | Fl l Ar label
255 .Ar device ...
256 .Xc
257 The
258 .Ic label
259 command allows the user to label any partitions that match the selection.
260 At least one of the following selection options must be specified.
261 .Pp
262 The
263 .Fl a
264 option specifies that all partitions should be labeled.
265 It is mutually exclusive with all other selection options.
266 .Pp
267 The
268 .Fl b Ar number
269 option selects the partition that starts at the given block number.
270 .Pp
271 The
272 .Fl i Ar index
273 option selects the partition with the given partition number.
274 Partition numbers start at 0.
275 .Pp
276 The
277 .Fl s Ar count
278 option selects all partitions that have the given size.
279 This can cause multiple partitions to be removed.
280 .Pp
281 The
282 .Fl t Ar type
283 option selects all partitions that have the given type.
284 The type is given as an UUID or by the aliases that the
285 .Ic add
286 command accepts.
287 This can cause multiple partitions to be removed.
288 .Pp
289 The
290 .Fl f Ar file
291 or
292 .Fl l Ar label
293 options specify the new label to be assigned to the selected partitions.
294 The
295 .Fl f Ar file
296 option is used to read the label from the specified file.
297 Only the first line is read from the file and the trailing newline
298 character is stripped.
299 If the file name is the dash or minus sign
300 .Pq Fl ,
301 the label is read from
302 the standard input.
303 The
304 .Fl l Ar label
305 option is used to specify the label in the command line.
306 The label is assumed to be encoded in UTF-8.
307 .\" ==== migrate ====
308 .It Nm Ic migrate Oo Fl fs Oc Ar device ...
309 The
310 .Ic migrate
311 command allows the user to migrate an MBR-based disk partitioning into a
312 GPT-based partitioning.
313 By default, the MBR is not migrated when it contains partitions of an unknown
314 type.
315 This can be overridden with the
316 .Fl f
317 option.
318 Specifying the
319 .Fl f
320 option will cause unknown partitions to be ignored and any data in it
321 to be lost.
322 .Pp
323 The
324 .Fl s
325 option prevents migrating
326 .Bx
327 disk labels into GPT partitions by creating
328 the GPT equivalent of a slice.
329 .\" ==== remove ====
330 .It Nm Ic remove Oo Fl a Oc Ar device ...
331 .It Xo
332 .Nm
333 .Ic remove
334 .Op Fl b Ar number
335 .Op Fl i Ar index
336 .Op Fl s Ar count
337 .Op Fl t Ar type
338 .Ar device ...
339 .Xc
340 The
341 .Ic remove
342 command allows the user to remove any and all partitions that match the
343 selection.
344 It uses the same selection options as the
345 .Ic label
346 command.
347 See above for a description of these options.
348 Partitions are removed by clearing the partition type.
349 No other information is changed.
350 .\" ==== show ====
351 .It Nm Ic show Oo Fl lu Oc Ar device ...
352 The
353 .Ic show
354 command displays the current partitioning on the listed devices and gives
355 an overall view of the disk contents.
356 With the
357 .Fl l
358 option the GPT partition label will be displayed instead of the GPT partition
359 type.
360 The option has no effect on non-GPT partitions.
361 With the
362 .Fl u
363 option the GPT partition type is displayed as an UUID instead of in a
364 user friendly form.
365 The
366 .Fl l
367 option takes precedence over the
368 .Fl u
369 option.
370 .El
371 .Sh FILES
372 .Bl -tag -width ".Pa /etc/defaults/uuids"
373 .It Pa /boot/boot0
374 The default
375 .Sq boot0
376 image.
377 .It Pa /etc/defaults/uuids
378 A list of UUIDs
379 and their symbolic names provided by the OS vendor.
380 .It Pa /etc/uuids
381 A list of UUIDs
382 and their symbolic names provided by the system administrator.
383 .El
384 .Sh EXAMPLES
385 To install an empty GPT on
386 .Pa ad6 :
387 .Pp
388 .Dl "gpt create ad6"
389 .Pp
390 GPT partitions are defined in number of sectors, the sector size is usually 512B,
391 which is assumed in the examples below, it can be found using:
392 .Pp
393 .Dl "gpt -v show ad6"
394 .Pp
395 To add a dummy GPT partition 0:
396 .Pp
397 .Dl "gpt add -i0 -s16 ad6"
398 .Pp
399 You might want to do this to not use slice 0 for data;
400 when GPT is not used on a disk, slice 0 is the compatibility slice,
401 which is used for
402 .Dq dangerously dedicated
403 disks.
404 For GPT slice 0 has no special meaning, it is just the first slice on the disk.
405 .Pp
406 To add a GPT partition of size approx. 100GB:
407 .Pp
408 .Dl "gpt add -s200000000 ad6"
409 .Pp
410 This will be GPT partition 1 as it is the first one free,
411 it will be accessible as
412 .Pa ad6s1 ,
413 which is also printed by the command.
414 The type will be
415 .Dq DragonFly Label64 ,
416 it will have to be set up by
417 .Xr disklabel64 8 .
418 .Pp
419 To add GPT partition 5 with type
420 .Dq DragonFly HAMMER
421 using the remaining free space:
422 .Bd -literal -offset indent
423 gpt add -i5 -t "DragonFly HAMMER" ad6
424 .Ed
425 .Pp
426 To print the contents of the GPT:
427 .Pp
428 .Dl "gpt show ad6"
429 .Ss Boot Setup
430 To setup a disk using GPT for booting, the steps below can be used.
431 System is copied from an already installed disk,
432 e.g.\& a hard disk or an install CD.
433 This example will setup disk
434 .Pa da1
435 with GPT for booting, using the
436 .Ic boot
437 command.
438 .Pp
439 .Em WARNING!
440 Any previous data on disk installed to will be deleted.
441 .Bd -literal -offset indent
442 gpt create -f da1
443 gpt boot da1
444 boot0cfg -s 2 da1
445 disklabel -B -r -w da1s0 auto
446 disklabel -e da1s0 # add `a: * * 4.2BSD', to add `a' partition
447 # with fstype `4.2BSD' covering whole slice
449 gpt add da1
450 disklabel64 -r -w da1s1 auto
451 disklabel64 -e da1s1 # add `b: 4G * swap', to add `b' partition
452 # with fstype `swap' and size 4GB,
453 # add `a: * * HAMMER', to add `a' partition
454 # with fstype `HAMMER' covering rest of slice
455 newfs_hammer -L ROOT /dev/da1s1a
456 mount_hammer /dev/da1s1a /mnt
458 newfs /dev/da1s0a
459 mkdir /mnt/boot
460 mount /dev/da1s0a /mnt/boot
462 cpdup / /mnt # copy each file system you need, e.g.
463 cpdup /boot /mnt/boot
464 cpdup /var /mnt/var
465 cpdup /var/tmp /mnt/var/tmp
466 cpdup /usr /mnt/usr
468 cd /mnt
469 vi etc/fstab # add `/dev/da1s1a / hammer rw',
470 # add `/dev/da1s1b none swap sw',
471 # add `/dev/da1s0a /boot ufs rw 1 1',
472 # delete lines for file systems cpdup'ed above
473 vi boot/loader.conf # add `vfs.root.mountfrom="hammer:da1s1a"'
474 cd
475 umount /mnt/boot
476 umount /mnt
477 .Ed
478 .Sh COMPATIBILITY
479 The GPT that
480 .Nm
481 manipulates is part of the EFI standard and is supported by many OSs.
482 GPT uses 64 bits to store number of sectors, this supports very large disks.
483 With the prevalent sector size of 512B this is 8 billion TB.
484 .Sh SEE ALSO
485 .Xr uuid 3 ,
486 .Xr disklabel64 5 ,
487 .Xr uuids 5 ,
488 .Xr boot0cfg 8 ,
489 .Xr disklabel 8 ,
490 .Xr disklabel64 8 ,
491 .Xr fdisk 8 ,
492 .Xr mount 8 ,
493 .Xr newfs 8 ,
494 .Xr newfs_hammer 8 ,
495 .Xr swapon 8
496 .Sh HISTORY
497 The
498 .Nm
499 utility appeared in
500 .Fx 5.0
501 for ia64.
502 It was imported to
503 .Dx 1.9 .
504 .Sh BUGS
505 The development of the
506 .Nm
507 utility is still work in progress.
508 Many necessary features are missing or partially implemented.
509 In practice this means that the manual page, supposed to describe these
510 features, is farther removed from being complete or useful.
511 As such, missing functionality is not even documented as missing.
512 However, it is believed that the currently present functionality is reliable
513 and stable enough that this tool can be used without bullet-proof footware if
514 one thinks one does not make mistakes.
515 .Pp
516 It is expected that the basic usage model does not change, but it is
517 possible that future versions will not be compatible in the strictest sense
518 of the word.
519 For example, the
520 .Fl p Ar count
521 option may be changed to a command option rather than a generic option.
522 There are only two commands that use it so there is a chance that the natural
523 tendency for people is to use it as a command option.
524 Also, options primarily intended for diagnostic or debug purposes may be
525 removed in future versions.
526 .Pp
527 Another possibility is that the current usage model is accompanied by
528 other interfaces to make the tool usable as a back-end.
529 This all depends on demand and thus feedback.
530 .Pp
531 The
532 .Ic migrate
533 command doesn't support
534 .Dx
535 partition types.