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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 , hammer, hammer2
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 .\" ==== init ====
240 .It Nm Ic init Fl f Oo Fl B Oc Ar device ...
241 The
242 .Ic init
243 command allows the user to create a new GPT similar
244 to the create command, but will also populate it with
245 a boot slice (s0) and a
246 .Dx
247 slice (s1).
248 The boot slice will be dos-formatted.
249 The disklabel will be left empty and ready to edit.
250 .Pp
251 Due to the destructive nature of this directive, the
252 .Fl f
253 option must also be specified.
254 .Pp
255 If the
256 .Fl B
257 option is specified, /boot/bootx64.efi will be copied into
258 the msdos slice (s0), and the disklabel will be initialized
259 with -B in addition to the normal -r -w.
260 .\" ==== label ====
261 .It Xo
262 .Nm
263 .Ic label
264 .Op Fl a
265 .Aq Fl f Ar file | Fl l Ar label
266 .Ar device ...
267 .Xc
268 .It Xo
269 .Nm
270 .Ic label
271 .Op Fl b Ar number
272 .Op Fl i Ar index
273 .Op Fl s Ar count
274 .Op Fl t Ar type
275 .Aq Fl f Ar file | Fl l Ar label
276 .Ar device ...
277 .Xc
278 The
279 .Ic label
280 command allows the user to label any partitions that match the selection.
281 At least one of the following selection options must be specified.
282 .Pp
283 The
284 .Fl a
285 option specifies that all partitions should be labeled.
286 It is mutually exclusive with all other selection options.
287 .Pp
288 The
289 .Fl b Ar number
290 option selects the partition that starts at the given block number.
291 .Pp
292 The
293 .Fl i Ar index
294 option selects the partition with the given partition number.
295 Partition numbers start at 0.
296 .Pp
297 The
298 .Fl s Ar count
299 option selects all partitions that have the given size.
300 This can cause multiple partitions to be removed.
301 .Pp
302 The
303 .Fl t Ar type
304 option selects all partitions that have the given type.
305 The type is given as an UUID or by the aliases that the
306 .Ic add
307 command accepts.
308 This can cause multiple partitions to be removed.
309 .Pp
310 The
311 .Fl f Ar file
312 or
313 .Fl l Ar label
314 options specify the new label to be assigned to the selected partitions.
315 The
316 .Fl f Ar file
317 option is used to read the label from the specified file.
318 Only the first line is read from the file and the trailing newline
319 character is stripped.
320 If the file name is the dash or minus sign
321 .Pq Fl ,
322 the label is read from
323 the standard input.
324 The
325 .Fl l Ar label
326 option is used to specify the label in the command line.
327 The label is assumed to be encoded in UTF-8.
328 .\" ==== migrate ====
329 .It Nm Ic migrate Oo Fl fs Oc Ar device ...
330 The
331 .Ic migrate
332 command allows the user to migrate an MBR-based disk partitioning into a
333 GPT-based partitioning.
334 By default, the MBR is not migrated when it contains partitions of an unknown
335 type.
336 This can be overridden with the
337 .Fl f
338 option.
339 Specifying the
340 .Fl f
341 option will cause unknown partitions to be ignored and any data in it
342 to be lost.
343 .Pp
344 The
345 .Fl s
346 option prevents migrating
347 .Bx
348 disk labels into GPT partitions by creating
349 the GPT equivalent of a slice.
350 .\" ==== remove ====
351 .It Nm Ic remove Oo Fl a Oc Ar device ...
352 .It Xo
353 .Nm
354 .Ic remove
355 .Op Fl b Ar number
356 .Op Fl i Ar index
357 .Op Fl s Ar count
358 .Op Fl t Ar type
359 .Ar device ...
360 .Xc
361 The
362 .Ic remove
363 command allows the user to remove any and all partitions that match the
364 selection.
365 It uses the same selection options as the
366 .Ic label
367 command.
368 See above for a description of these options.
369 Partitions are removed by clearing the partition type.
370 No other information is changed.
371 .\" ==== show ====
372 .It Nm Ic show Oo Fl lu Oc Ar device ...
373 The
374 .Ic show
375 command displays the current partitioning on the listed devices and gives
376 an overall view of the disk contents.
377 With the
378 .Fl l
379 option the GPT partition label will be displayed instead of the GPT partition
380 type.
381 The option has no effect on non-GPT partitions.
382 With the
383 .Fl u
384 option the GPT partition type is displayed as an UUID instead of in a
385 user friendly form.
386 The
387 .Fl l
388 option takes precedence over the
389 .Fl u
390 option.
391 .El
392 .Sh FILES
393 .Bl -tag -width ".Pa /etc/defaults/uuids"
394 .It Pa /boot/boot0
395 The default
396 .Sq boot0
397 image.
398 .It Pa /etc/defaults/uuids
399 A list of UUIDs
400 and their symbolic names provided by the OS vendor.
401 .It Pa /etc/uuids
402 A list of UUIDs
403 and their symbolic names provided by the system administrator.
404 .El
405 .Sh EXAMPLES
406 To install an empty GPT on
407 .Pa ad6 :
408 .Pp
409 .Dl "gpt create ad6"
410 .Pp
411 GPT partitions are defined in number of sectors, the sector size is usually 512B,
412 which is assumed in the examples below, it can be found using:
413 .Pp
414 .Dl "gpt -v show ad6"
415 .Pp
416 To add a dummy GPT partition 0:
417 .Pp
418 .Dl "gpt add -i0 -s16 ad6"
419 .Pp
420 You might want to do this to not use slice 0 for data;
421 when GPT is not used on a disk, slice 0 is the compatibility slice,
422 which is used for
423 .Dq dangerously dedicated
424 disks.
425 For GPT slice 0 has no special meaning, it is just the first slice on the disk.
426 .Pp
427 To add a GPT partition of size approx. 100GB:
428 .Pp
429 .Dl "gpt add -s200000000 ad6"
430 .Pp
431 This will be GPT partition 1 as it is the first one free,
432 it will be accessible as
433 .Pa ad6s1 ,
434 which is also printed by the command.
435 The type will be
436 .Dq DragonFly Label64 ,
437 it will have to be set up by
438 .Xr disklabel64 8 .
439 .Pp
440 To add GPT partition 5 with type
441 .Dq DragonFly HAMMER
442 using the remaining free space:
443 .Bd -literal -offset indent
444 gpt add -i5 -t "DragonFly HAMMER" ad6
445 .Ed
446 .Pp
447 To print the contents of the GPT:
448 .Pp
449 .Dl "gpt show ad6"
450 .Ss Boot Setup
451 To setup a disk using GPT for booting, the steps below can be used.
452 System is copied from an already installed disk,
453 e.g.\& a hard disk or an install CD.
454 This example will setup disk
455 .Pa da1
456 with GPT for booting, using the
457 .Ic boot
458 command.
459 .Pp
460 .Em WARNING!
461 Any previous data on disk installed to will be deleted.
462 .Bd -literal -offset indent
463 gpt create -f da1
464 gpt boot da1
465 boot0cfg -s 2 da1
466 disklabel -B -r -w da1s0 auto
467 disklabel -e da1s0 # add `a: * * 4.2BSD', to add `a' partition
468 # with fstype `4.2BSD' covering whole slice
470 gpt add da1
471 disklabel64 -r -w da1s1 auto
472 disklabel64 -e da1s1 # add `b: 4G * swap', to add `b' partition
473 # with fstype `swap' and size 4GB,
474 # add `a: * * HAMMER', to add `a' partition
475 # with fstype `HAMMER' covering rest of slice
476 newfs_hammer -L ROOT /dev/da1s1a
477 mount_hammer /dev/da1s1a /mnt
479 newfs /dev/da1s0a
480 mkdir /mnt/boot
481 mount /dev/da1s0a /mnt/boot
483 cpdup / /mnt # copy each file system you need, e.g.
484 cpdup /boot /mnt/boot
485 cpdup /var /mnt/var
486 cpdup /var/tmp /mnt/var/tmp
487 cpdup /usr /mnt/usr
489 cd /mnt
490 vi etc/fstab # add `/dev/da1s1a / hammer rw',
491 # add `/dev/da1s1b none swap sw',
492 # add `/dev/da1s0a /boot ufs rw 1 1',
493 # delete lines for file systems cpdup'ed above
494 vi boot/loader.conf # add `vfs.root.mountfrom="hammer:da1s1a"'
495 cd
496 umount /mnt/boot
497 umount /mnt
498 .Ed
499 .Sh COMPATIBILITY
500 The GPT that
501 .Nm
502 manipulates is part of the EFI standard and is supported by many OSs.
503 GPT uses 64 bits to store number of sectors, this supports very large disks.
504 With the prevalent sector size of 512B this is 8 billion TB.
505 .Sh SEE ALSO
506 .Xr uuid 3 ,
507 .Xr disklabel64 5 ,
508 .Xr uuids 5 ,
509 .Xr boot0cfg 8 ,
510 .Xr disklabel 8 ,
511 .Xr disklabel64 8 ,
512 .Xr fdisk 8 ,
513 .Xr mount 8 ,
514 .Xr newfs 8 ,
515 .Xr newfs_hammer 8 ,
516 .Xr swapon 8
517 .Sh HISTORY
518 The
519 .Nm
520 utility appeared in
521 .Fx 5.0
522 for ia64.
523 It was imported to
524 .Dx 1.9 .
525 .Sh BUGS
526 The development of the
527 .Nm
528 utility is still work in progress.
529 Many necessary features are missing or partially implemented.
530 In practice this means that the manual page, supposed to describe these
531 features, is farther removed from being complete or useful.
532 As such, missing functionality is not even documented as missing.
533 However, it is believed that the currently present functionality is reliable
534 and stable enough that this tool can be used without bullet-proof footware if
535 one thinks one does not make mistakes.
536 .Pp
537 It is expected that the basic usage model does not change, but it is
538 possible that future versions will not be compatible in the strictest sense
539 of the word.
540 For example, the
541 .Fl p Ar count
542 option may be changed to a command option rather than a generic option.
543 There are only two commands that use it so there is a chance that the natural
544 tendency for people is to use it as a command option.
545 Also, options primarily intended for diagnostic or debug purposes may be
546 removed in future versions.
547 .Pp
548 Another possibility is that the current usage model is accompanied by
549 other interfaces to make the tool usable as a back-end.
550 This all depends on demand and thus feedback.
551 .Pp
552 The
553 .Ic migrate
554 command doesn't support
555 .Dx
556 partition types.