1SGDISK(8) GPT fdisk Manual SGDISK(8)
2
6 sgdisk - Command-line GUID partition table (GPT) manipulator for Linux
7 and Unix
8
10 sgdisk [ options ] device
11
14 GPT fdisk is a text-mode menu-driven package for creation and manipula‐
15 tion of partition tables. It consists of two programs: the text-mode
16 interactive gdisk and the command-line sgdisk. Either program will
17 automatically convert an old-style Master Boot Record (MBR) partition
18 table or BSD disklabel stored without an MBR carrier partition to the
19 newer Globally Unique Identifier (GUID) Partition Table (GPT) format,
20 or will load a GUID partition table. This man page documents the com‐
21 mand-line sgdisk program.
22 Some advanced data manipulation and recovery options require you to
24 understand the distinctions between the main and backup data, as well
25 as between the GPT headers and the partition tables. For information on
26 MBR vs. GPT, as well as GPT terminology and structure, see the extended
27 gdisk documentation at http://www.rodsbooks.com/gdisk/ or consult
28 Wikipedia.
29 The sgdisk program employs a user interface that's based entirely on
31 the command line, making it suitable for use in scripts or by experts
32 who want to make one or two quick changes to a disk. (The program may
33 query the user when certain errors are encountered, though.) The pro‐
34 gram's name is based on sfdisk, but the user options of the two pro‐
35 grams are entirely different from one another.
36 Ordinarily, sgdisk operates on disk device files, such as /dev/sda or
38 /dev/hda under Linux, /dev/disk0 under Mac OS X, or /dev/ad0 or
39 /dev/da0 under FreeBSD. The program can also operate on disk image
40 files, which can be either copies of whole disks (made with dd, for
41 instance) or raw disk images used by emulators such as QEMU or VMWare.
42 Note that only raw disk images are supported; sgdisk cannot work on
43 compressed or other advanced disk image formats.
44 The MBR partitioning system uses a combination of cylinder/head/sector
46 (CHS) addressing and logical block addressing (LBA). The former is
47 klunky and limiting. GPT drops CHS addressing and uses 64-bit LBA mode
48 exclusively. Thus, GPT data structures, and therefore sgdisk, do not
49 need to deal with CHS geometries and all the problems they create.
50 For best results, you should use an OS-specific partition table program
52 whenever possible. For example, you should make Mac OS X partitions
53 with the Mac OS X Disk Utility program and Linux partitions with the
54 Linux gdisk, sgdisk, or GNU Parted programs.
55 Upon start, sgdisk attempts to identify the partition type in use on
57 the disk. If it finds valid GPT data, sgdisk will use it. If sgdisk
58 finds a valid MBR or BSD disklabel but no GPT data, it will attempt to
59 convert the MBR or disklabel into GPT form. (BSD disklabels are likely
60 to have unusable first and/or final partitions because they overlap
61 with the GPT data structures, though.) GPT fdisk can identify, but not
62 use data in, Apple Partition Map (APM) disks, which are used on 680x0-
63 and PowerPC-based Macintoshes. If you specify any option that results
64 in changes to an MBR or BSD disklabel, sgdisk ignores those changes
65 unless the -g (--mbrtogpt), -z (--zap), or -Z (--zap-all) option is
66 used. If you use the -g option, sgdisk replaces the MBR or disklabel
67 with a GPT. This action is potentially dangerous! Your system may
68 become unbootable, and partition type codes may become corrupted if the
69 disk uses unrecognized type codes. Boot problems are particularly
70 likely if you're multi-booting with any GPT-unaware OS.
71 The MBR-to-GPT conversion will leave at least one gap in the partition
73 numbering if the original MBR used logical partitions. These gaps are
74 harmless, but you can eliminate them by using the -s (--sort) option,
75 if you like. (Doing this may require you to update your /etc/fstab
76 file.)
77 When creating a fresh partition table, certain considerations may be in
79 order:
80 * For data (non-boot) disks, and for boot disks used on BIOS-based
83 computers with GRUB as the boot loader, partitions may be cre‐
84 ated in whatever order and in whatever sizes are desired.
85 * Boot disks for EFI-based systems require an EFI System Partition
88 (sgdisk internal code 0xEF00) formatted as FAT-32. The recom‐
89 mended size of this partition is between 100 and 300 MiB.
90 Boot-related files are stored here. (Note that GNU Parted iden‐
91 tifies such partitions as having the "boot flag" set.)
92 * Some boot loaders for BIOS-based systems make use of a BIOS Boot
95 Partition (sgdisk internal code 0xEF02), in which the secondary
96 boot loader is stored, possibly without the benefit of a
97 filesystem. This partition can typically be quite small (roughly
98 32 to 200 KiB), but you should consult your boot loader documen‐
99 tation for details.
100 * If Windows is to boot from a GPT disk, a partition of type Mi‐
103 crosoft Reserved (sgdisk internal code 0x0C01) is recommended.
104 This partition should be about 128 MiB in size. It ordinarily
105 follows the EFI System Partition and immediately precedes the
106 Windows data partitions. (Note that GNU Parted creates all FAT
107 partitions as this type, which actually makes the partition
108 unusable for normal file storage in both Windows and Mac OS X.)
109 * Some OSes' GPT utilities create some blank space (typically 128
112 MiB) after each partition. The intent is to enable future disk
113 utilities to use this space. Such free space is not required of
114 GPT disks, but creating it may help in future disk maintenance.
115
118 Some options take no arguments, others take one argument (typically a
119 partition number), and others take compound arguments with colon delim‐
120 itation. For instance, -n (--new) takes a partition number, a starting
121 sector number, and an ending sector number, as in sgdisk -n
122 2:2000:50000 /dev/sdc, which creates a new partition, numbered 2,
123 starting at sector 2000 an ending at sector 50,000, on /dev/sdc.
124 Unrelated options may be combined; however, some such combinations will
126 be nonsense (such as deleting a partition and then changing its GUID
127 type code). sgdisk interprets options in the order in which they're
128 entered, so effects can vary depending on order. For instance, sgdisk
129 -s -d 2 sorts the partition table entries and then deletes partition 2
130 from the newly-sorted list; but sgdisk -d 2 -s deletes the original
131 partition 2 and then sorts the modified partition table.
132 Error checking and opportunities to correct mistakes in sgdisk are min‐
134 imal. Although the program endeavors to keep the GPT data structures
135 legal, it does not prompt for verification before performing its
136 actions. Unless you require a command-line-driven program, you should
137 use the interactive gdisk instead of sgdisk, since gdisk allows you to
138 quit without saving your changes, should you make a mistake.
139 Although sgdisk is based on the same partition-manipulation code as
141 gdisk, sgdisk implements fewer features than its interactive sibling.
142 Options available in sgdisk are:
143 -a, --set-alignment=value
146 Set the sector alignment multiple. GPT fdisk aligns the start of
147 partitions to sectors that are multiples of this value, which
148 defaults to 2048 on freshly formatted disks. This alignment
149 value is necessary to obtain optimum performance with Western
150 Digital Advanced Format and similar drives with larger physical
151 than logical sector sizes, with some types of RAID arrays, and
152 with SSD devices.
153 -A, --attributes=list|[partnum:show|or|nand|xor|=|set|clear|tog‐
156 gle|get[:bitnum|hexbitmask]]
157 View or set partition attributes. Use list to see defined
158 (known) attribute values. Omit the partition number (and even
159 the device filename) when using this option. The others require
160 a partition number. The show and get options show the current
161 attribute settings (all attributes or for a particular bit,
162 respectively). The or, nand, xor, =, set, clear, and toggle
163 options enable you to change the attribute bit value. The set,
164 clear, toggle, and get options work on a bit number; the others
165 work on a hexadecimal bit mask. For example, type sgdisk -A
166 4:set:2 /dev/sdc to set the bit 2 attribute (legacy BIOS
167 bootable) on partition 4 on /dev/sdc.
168 -b, --backup=file
171 Save partition data to a backup file. You can back up your cur‐
172 rent in-memory partition table to a disk file using this option.
173 The resulting file is a binary file consisting of the protective
174 MBR, the main GPT header, the backup GPT header, and one copy of
175 the partition table, in that order. Note that the backup is of
176 the current in-memory data structures, so if you launch the pro‐
177 gram, make changes, and then use this option, the backup will
178 reflect your changes. If the GPT data structures are damaged,
179 the backup may not accurately reflect the damaged state;
180 instead, they will reflect GPT fdisk's first-pass interpretation
181 of the GPT.
182 -c, --change-name=partnum:name
185 Change the GPT name of a partition. This name is encoded as a
186 UTF-16 string, but proper entry and display of anything beyond
187 basic ASCII values requires suitable locale and font support.
188 For the most part, Linux ignores the partition name, but it may
189 be important in some OSes. If you want to set a name that
190 includes a space, enclose it in quotation marks, as in sgdisk -c
191 1:"Sample Name" /dev/sdb. Note that the GPT name of a partition
192 is distinct from the filesystem name, which is encoded in the
193 filesystem's data structures.
194 -C, --recompute-chs
197 Recompute CHS values in protective or hybrid MBR. This option
198 can sometimes help if a disk utility, OS, or BIOS doesn't like
199 the CHS values used by the partitions in the protective or
200 hybrid MBR. In particular, the GPT specification requires a CHS
201 value of 0xFFFFFF for over-8GiB partitions, but this value is
202 technically illegal by the usual standards. Some BIOSes hang if
203 they encounter this value. This option will recompute a more
204 normal CHS value -- 0xFEFFFF for over-8GiB partitions, enabling
205 these BIOSes to boot.
206 -d, --delete=partnum
209 Delete a partition. This action deletes the entry from the par‐
210 tition table but does not disturb the data within the sectors
211 originally allocated to the partition on the disk. If a corre‐
212 sponding hybrid MBR partition exists, gdisk deletes it, as well,
213 and expands any adjacent 0xEE (EFI GPT) MBR protective partition
214 to fill the new free space.
215 -D, --display-alignment
218 Display current sector alignment value. Partitions will be cre‐
219 ated on multiples of the sector value reported by this option.
220 You can change the alignment value with the -a option.
221 e, --move-second-header
224 Move backup GPT data structures to the end of the disk. Use this
225 option if you've added disks to a RAID array, thus creating a
226 virtual disk with space that follows the backup GPT data struc‐
227 tures. This command moves the backup GPT data structures to the
228 end of the disk, where they belong.
229 -E, --end-of-largest
232 Displays the sector number of the end of the largest available
233 block of sectors on the disk. A script may store this value and
234 pass it back as part of -n's option to create a partition. If no
235 unallocated sectors are available, this function returns the
236 value 0.
237 -f, --first-in-largest
240 Displays the sector number of the start of the largest available
241 block of sectors on the disk. A script may store this value and
242 pass it back as part of -n's option to create a partition. If no
243 unallocated sectors are available, this function returns the
244 value 0. Note that this parameter is blind to partition align‐
245 ment; when you actually create a partition, its start point
246 might be changed from this value.
247 -F, --first-aligned-in-largest
250 Similar to -f (--first-in-largest), except returns the sector
251 number with the current alignment correction applied. Use this
252 function if you need to compute the actual partition start point
253 rather than a theoretical start point or the actual start point
254 if you set the alignment value to 1.
255 -g, --mbrtogpt
258 Convert an MBR or BSD disklabel disk to a GPT disk. As a safety
259 measure, use of this option is required on MBR or BSD disklabel
260 disks if you intend to save your changes, in order to prevent
261 accidentally damaging such disks.
262 -G, --randomize-guids
265 Randomize the disk's GUID and all partitions' unique GUIDs (but
266 not their partition type code GUIDs). This function may be used
267 after cloning a disk in order to render all GUIDs once again
268 unique.
269 -h, --hybrid
272 Create a hybrid MBR. This option takes from one to three parti‐
273 tion numbers, separated by colons, as arguments. The created
274 hybrid MBR places an EFI GPT (type 0xEE) partition first in the
275 table, followed by the partition(s) you specify. Their type
276 codes are based on the GPT fdisk type codes divided by 0x0100,
277 which is usually correct for Windows partitions. If the
278 active/bootable flag should be set, you must do so in another
279 program, such as fdisk. The gdisk program offers additional
280 hybrid MBR creation options.
281 -i, --info=partnum
284 Show detailed partition information. The summary information
285 produced by the -p command necessarily omits many details, such
286 as the partition's unique GUID and the translation of sgdisk's
287 internal partition type code to a plain type name. The -i option
288 displays this information for a single partition.
289 -l, --load-backup=file
292 Load partition data from a backup file. This option is the
293 reverse of the -b option. Note that restoring partition data
294 from anything but the original disk is not recommended. This
295 option will work even if the disk's original partition table is
296 bad; however, most other options on the same command line will
297 be ignored.
298 -L, --list-types
301 Display a summary of partition types. GPT uses a GUID to iden‐
302 tify partition types for particular OSes and purposes. For ease
303 of data entry, sgdisk compresses these into two-byte (four-digit
304 hexadecimal) values that are related to their equivalent MBR
305 codes. Specifically, the MBR code is multiplied by hexadecimal
306 0x0100. For instance, the code for Linux swap space in MBR is
307 0x82, and it's 0x8200 in gdisk. A one-to-one correspondence is
308 impossible, though. Most notably, the codes for all varieties of
309 FAT and NTFS partition correspond to a single GPT code (entered
310 as 0x0700 in sgdisk). Some OSes use a single MBR code but employ
311 many more codes in GPT. For these, sgdisk adds code numbers
312 sequentially, such as 0xa500 for a FreeBSD disklabel, 0xa501 for
313 FreeBSD boot, 0xa502 for FreeBSD swap, and so on. Note that
314 these two-byte codes are unique to gdisk and sgdisk. This option
315 does not require you to specify a valid disk device filename.
316 -m, --gpttombr
319 Convert disk from GPT to MBR form. This option takes from one to
320 four partition numbers, separated by colons, as arguments. Their
321 type codes are based on the GPT fdisk type codes divided by
322 0x0100. If the active/bootable flag should be set, you must do
323 so in another program, such as fdisk. The gdisk program offers
324 additional MBR conversion options. It is not possible to convert
325 more than four partitions from GPT to MBR form or to convert
326 partitions that start above the 2TiB mark or that are larger
327 than 2TiB.
328 -n, --new=partnum:start:end
331 Create a new partition. You enter a partition number, starting
332 sector, and an ending sector. Both start and end sectors can be
333 specified in absolute terms as sector numbers or as positions
334 measured in kibibytes (K), mebibytes (M), gibibytes (G),
335 tebibytes (T), or pebibytes (P); for instance, 40M specifies a
336 position 40MiB from the start of the disk. You can specify loca‐
337 tions relative to the start or end of the specified default
338 range by preceding the number by a '+' or '-' symbol, as in +2G
339 to specify a point 2GiB after the default start sector, or -200M
340 to specify a point 200MiB before the last available sector. A
341 start or end value of 0 specifies the default value, which is
342 the start of the largest available block for the start sector
343 and the end of the same block for the end sector. A partnum
344 value of 0 causes the program to use the first available parti‐
345 tion number. Subsequent uses of the -A, -c, -t, and -u options
346 may also use 0 to refer to the same partition.
347 -N, --largest-new=num
350 Create a new partition that fills the largest available block of
351 space on the disk. Note that if used on a completely blank disk,
352 this is likely to result in a sector-moved warning, since the
353 first available sector (normally 34) doesn't fall on a 2048-sec‐
354 tor boundary (the default for alignment). You can use the -a
355 (--set-alignment) option to adjust the alignment, if desired. A
356 num value of 0 causes the program to use the first available
357 partition number.
358 -o, --clear
361 Clear out all partition data. This includes GPT header data, all
362 partition definitions, and the protective MBR. Note that this
363 operation will, like most other operations, fail on a damaged
364 disk. If you want to prepare a disk you know to be damaged for
365 GPT use, you should first wipe it with -Z and then partition it
366 normally. This option will work even if the disk's original par‐
367 tition table is bad; however, most other options on the same
368 command line will be ignored.
369 -p, --print
372 Display basic partition summary data. This includes partition
373 numbers, starting and ending sector numbers, partition sizes,
374 sgdisk's partition types codes, and partition names. For addi‐
375 tional information, use the -i (--info) option.
376 -P, --pretend
379 Pretend to make specified changes. In-memory GPT data structures
380 are altered according to other parameters, but changes are not
381 written to disk.
382 -r, --transpose
385 Swap two partitions' entries in the partition table. One or both
386 partitions may be empty, although swapping two empty partitions
387 is pointless. For instance, if partitions 1-4 are defined,
388 transposing 1 and 5 results in a table with partitions numbered
389 from 2-5. Transposing partitions in this way has no effect on
390 their disk space allocation; it only alters their order in the
391 partition table.
392 -R, --replicate=second_device_filename
395 Replicate the main device's partition table on the specified
396 second device. Note that the replicated partition table is an
397 exact copy, including all GUIDs; if the device should have its
398 own unique GUIDs, you should use the -G option on the new disk.
399 -s, --sort
402 Sort partition entries. GPT partition numbers need not match the
403 order of partitions on the disk. If you want them to match, you
404 can use this option. Note that some partitioning utilities sort
405 partitions whenever they make changes. Such changes will be
406 reflected in your device filenames, so you may need to edit
407 /etc/fstab if you use this option.
408 -t, --typecode=partnum:{hexcode|GUID}
411 Change a single partition's type code. You enter the type code
412 using either a two-byte hexadecimal number, as described ear‐
413 lier, or a fully-specified GUID value, such as
414 EBD0A0A2-B9E5-4433-87C0-68B6B72699C7.
415 -T, --transform-bsd=partnum
418 Transform BSD partitions into GPT partitions. This option works
419 on BSD disklabels held within GPT (or converted MBR) partitions.
420 Converted partitions' type codes are likely to need manual
421 adjustment. sgdisk will attempt to convert BSD disklabels stored
422 on the main disk when launched, but this conversion is likely to
423 produce first and/or last partitions that are unusable. The many
424 BSD variants means that the probability of sgdisk being unable
425 to convert a BSD disklabel is high compared to the likelihood of
426 problems with an MBR conversion.
427 -u, --partition-guid=partnum:guid
430 Set the partition unique GUID for an individual partition. The
431 GUID may be a complete GUID or 'R' to set a random GUID.
432 -U, --disk-guid=guid
435 Set the GUID for the disk. The GUID may be a complete GUID or
436 'R' to set a random GUID.
437 --usage
440 Print a brief summary of available options.
441 -v, --verify
444 Verify disk. This option checks for a variety of problems, such
445 as incorrect CRCs and mismatched main and backup data. This
446 option does not automatically correct most problems, though; for
447 that, you must use options on the recovery & transformation
448 menu. If no problems are found, this command displays a summary
449 of unallocated disk space. This option will work even if the
450 disk's original partition table is bad; however, most other
451 options on the same command line will be ignored.
452 -V, --version
455 Display program version information. This option may be used
456 without specifying a device filename.
457 -z, --zap
460 Zap (destroy) the GPT data structures and then exit. Use this
461 option if you want to repartition a GPT disk using fdisk or some
462 other GPT-unaware program. This option destroys only the GPT
463 data structures; it leaves the MBR intact. This makes it useful
464 for wiping out GPT data structures after a disk has been repar‐
465 titioned for MBR using a GPT-unaware utility; however, there's a
466 risk that it will damage boot loaders or even the start of the
467 first or end of the last MBR partition. If you use it on a valid
468 GPT disk, the MBR will be left with an inappropriate EFI GPT
469 (0xEE) partition definition, which you can delete using another
470 utility.
471 -Z, --zap-all
474 Zap (destroy) the GPT and MBR data structures and then exit.
475 This option works much like -z, but as it wipes the MBR as well
476 as the GPT, it's more suitable if you want to repartition a disk
477 after using this option, and completely unsuitable if you've
478 already repartitioned the disk.
479 -?, --help
482 Print a summary of options.
483
486 sgdisk returns various values depending on its success or failure:
487 0 Normal program execution
490 1 Too few arguments
493 2 An error occurred while reading the partition table
496 3 Non-GPT disk detected and no -g option
499 4 An error prevented saving changes
502 5 An error occurred while reading standard input (should never
505 occur with sgdisk, but may with gdisk)
506 8 Disk replication operation (-R) failed
509
512 As of March 2014 (version 0.8.10), sgdisk should be considered beta
513 software. Known bugs and limitations include:
514 * The program compiles correctly only on Linux, FreeBSD, and Mac
517 OS X. Linux versions for x86-64 (64-bit), x86 (32-bit), and Pow‐
518 erPC (32-bit) have been tested, with the x86-64 version having
519 seen the most testing.
520 * The FreeBSD version of the program can't write changes to the
523 partition table to a disk when existing partitions on that disk
524 are mounted. (The same problem exists with many other FreeBSD
525 utilities, such as gpt, fdisk, and dd.) This limitation can be
526 overcome by typing sysctl kern.geom.debugflags=16 at a shell
527 prompt.
528 * The fields used to display the start and end sector numbers for
531 partitions in the -p option are 14 characters wide. This trans‐
532 lates to a limitation of about 45 PiB. On larger disks, the dis‐
533 played columns will go out of alignment.
534 * The program can load only up to 128 partitions (4 primary parti‐
537 tions and 124 logical partitions) when converting from MBR for‐
538 mat. This limit can be raised by changing the #define
539 MAX_MBR_PARTS line in the basicmbr.h source code file and recom‐
540 piling; however, such a change will require using a
541 larger-than-normal partition table. (The limit of 128 partitions
542 was chosen because that number equals the 128 partitions sup‐
543 ported by the most common partition table size.)
544 * Converting from MBR format sometimes fails because of insuffi‐
547 cient space at the start or (more commonly) the end of the disk.
548 Resizing the partition table (using the 's' option in the
549 experts' menu) can sometimes overcome this problem; however, in
550 extreme cases it may be necessary to resize a partition using
551 GNU Parted or a similar tool prior to conversion with gdisk.
552 * MBR conversions work only if the disk has correct LBA partition
555 descriptors. These descriptors should be present on any disk
556 over 8 GiB in size or on smaller disks partitioned with any but
557 very ancient software.
558 * BSD disklabel support can create first and/or last partitions
561 that overlap with the GPT data structures. This can sometimes be
562 compensated by adjusting the partition table size, but in
563 extreme cases the affected partition(s) may need to be deleted.
564 * Because of the highly variable nature of BSD disklabel struc‐
567 tures, conversions from this form may be unreliable -- parti‐
568 tions may be dropped, converted in a way that creates overlaps
569 with other partitions, or converted with incorrect start or end
570 values. Use this feature with caution!
571 * Booting after converting an MBR or BSD disklabel disk is likely
574 to be disrupted. Sometimes re-installing a boot loader will fix
575 the problem, but other times you may need to switch boot load‐
576 ers. Except on EFI-based platforms, Windows through at least
577 Windows 7 RC doesn't support booting from GPT disks. Creating a
578 hybrid MBR (using the 'h' option on the recovery & transforma‐
579 tion menu) or abandoning GPT in favor of MBR may be your only
580 options in this case.
581
584 Primary author: Roderick W. Smith (rodsmith@rodsbooks.com)
585 Contributors:
587 * Yves Blusseau (1otnwmz02@sneakemail.com)
589 * David Hubbard (david.c.hubbard@gmail.com)
591 * Justin Maggard (justin.maggard@netgear.com)
593 * Dwight Schauer (dschauer@ti.com)
595 * Florian Zumbiehl (florz@florz.de)
597
601 cfdisk (8), cgdisk (8), fdisk (8), gdisk (8), mkfs (8), parted (8),
602 sfdisk (8) fixparts (8)
603 http://en.wikipedia.org/wiki/GUID_Partition_Table
605 http://developer.apple.com/technotes/tn2006/tn2166.html
607 http://www.rodsbooks.com/gdisk/
609
612 The sgdisk command is part of the GPT fdisk package and is available
613 from Rod Smith.
614Roderick W. Smith 0.8.10 SGDISK(8)