1GDISK(8) GPT fdisk Manual GDISK(8)
2
6 gdisk - Interactive GUID partition table (GPT) manipulator
7
9 gdisk [ -l ] device
10
13 GPT fdisk (aka gdisk) is a text-mode menu-driven program for creation
14 and manipulation of partition tables. It will automatically convert an
15 old-style Master Boot Record (MBR) partition table or BSD disklabel
16 stored without an MBR carrier partition to the newer Globally Unique
17 Identifier (GUID) Partition Table (GPT) format, or will load a GUID
18 partition table. When used with the -l command-line option, the program
19 displays the current partition table and then exits.
20 GPT fdisk operates mainly on the GPT headers and partition tables; how‐
22 ever, it can and will generate a fresh protective MBR, when required.
23 (Any boot loader code in the protective MBR will not be disturbed.) If
24 you've created an unusual protective MBR, such as a hybrid MBR created
25 by gptsync or gdisk's own hybrid MBR creation feature, this should not
26 be disturbed by most ordinary actions. Some advanced data recovery
27 options require you to understand the distinctions between the main and
28 backup data, as well as between the GPT headers and the partition
29 tables. For information on MBR vs. GPT, as well as GPT terminology and
30 structure, see the extended gdisk documentation at http://www.rods‐
31 books.com/gdisk/ or consult Wikipedia.
32 The gdisk program employs a user interface similar to that of Linux's
34 fdisk, but gdisk modifies GPT partitions. It also has the capability of
35 transforming MBR partitions or BSD disklabels into GPT partitions. Like
36 the original fdisk program, gdisk does not modify disk structures until
37 you explicitly write them to disk, so if you make a mistake, you can
38 exit from the program with the 'q' option to leave your partitions
39 unmodified.
40 Ordinarily, gdisk operates on disk device files, such as /dev/sda or
42 /dev/hda under Linux, /dev/disk0 under Mac OS X, or /dev/ad0 or
43 /dev/da0 under FreeBSD. The program can also operate on disk image
44 files, which can be either copies of whole disks (made with dd, for
45 instance) or raw disk images used by emulators such as QEMU or VMWare.
46 Note that only raw disk images are supported; gdisk cannot work on com‐
47 pressed or other advanced disk image formats.
48 The MBR partitioning system uses a combination of cylinder/head/sector
50 (CHS) addressing and logical block addressing (LBA). The former is
51 klunky and limiting. GPT drops CHS addressing and uses 64-bit LBA mode
52 exclusively. Thus, GPT data structures, and therefore gdisk, do not
53 need to deal with CHS geometries and all the problems they create.
54 Users of fdisk will note that gdisk lacks the options and limitations
55 associated with CHS geometries.
56 For best results, you should use an OS-specific partition table program
58 whenever possible. For example, you should make Mac OS X partitions
59 with the Mac OS X Disk Utility program and Linux partitions with the
60 Linux gdisk or GNU Parted program.
61 Upon start, gdisk attempts to identify the partition type in use on the
63 disk. If it finds valid GPT data, gdisk will use it. If gdisk finds a
64 valid MBR or BSD disklabel but no GPT data, it will attempt to convert
65 the MBR or disklabel into GPT form. (BSD disklabels are likely to have
66 unusable first and/or final partitions because they overlap with the
67 GPT data structures, though.) GPT fdisk can identify, but not use data
68 in, Apple Partition Map (APM) disks, which are used on 680x0- and Pow‐
69 erPC-based Macintoshes. Upon exiting with the 'w' option, gdisk
70 replaces the MBR or disklabel with a GPT. This action is potentially
71 dangerous! Your system may become unbootable, and partition type codes
72 may become corrupted if the disk uses unrecognized type codes. Boot
73 problems are particularly likely if you're multi-booting with any
74 GPT-unaware OS. If you mistakenly launch gdisk on an MBR disk, you can
75 safely exit the program without making any changes by using the 'q'
76 option.
77 The MBR-to-GPT conversion will leave at least one gap in the partition
79 numbering if the original MBR used logical partitions. These gaps are
80 harmless, but you can eliminate them by using the 's' option, if you
81 like. (Doing this may require you to update your /etc/fstab file.)
82 When creating a fresh partition table, certain considerations may be in
84 order:
85 * For data (non-boot) disks, and for boot disks used on BIOS-based
88 computers with GRUB as the boot loader, partitions may be cre‐
89 ated in whatever order and in whatever sizes are desired.
90 * Boot disks for EFI-based systems require an EFI System Partition
93 (gdisk internal code 0xEF00) formatted as FAT-32. The recom‐
94 mended size of this partition is between 100 and 300 MiB.
95 Boot-related files are stored here. (Note that GNU Parted iden‐
96 tifies such partitions as having the "boot flag" set.)
97 * Some boot loaders for BIOS-based systems make use of a BIOS Boot
100 Partition (gdisk internal code 0xEF02), in which the secondary
101 boot loader is stored, possibly without the benefit of a
102 filesystem. (GRUB2 may optionally use such a partition.) This
103 partition can typically be quite small (roughly 32 to 200 KiB),
104 but you should consult your boot loader documentation for
105 details.
106 * If Windows is to boot from a GPT disk, a partition of type Mi‐
109 crosoft Reserved (gdisk internal code 0x0C01) is recommended.
110 This partition should be about 128 MiB in size. It ordinarily
111 follows the EFI System Partition and immediately precedes the
112 Windows data partitions. (Note that old versions of GNU Parted
113 create all FAT partitions as this type, which actually makes the
114 partition unusable for normal file storage in both Windows and
115 Mac OS X.)
116 * Some OSes' GPT utilities create some blank space (typically 128
119 MiB) after each partition. The intent is to enable future disk
120 utilities to use this space. Such free space is not required of
121 GPT disks, but creating it may help in future disk maintenance.
122 You can use GPT fdisk's relative partition positioning option
123 (specifying the starting sector as '+128M', for instance) to
124 simplify creating such gaps.
125
128 -l List the partition tables for the specified devices and then
129 exit.
130 Most interactions with gdisk occur with its interactive text-mode
132 menus. Three menus exist: the main menu, the recovery & transformation
133 menu, and the experts' menu. The main menu provides the functions that
134 are most likely to be useful for typical partitioning tasks, such as
135 creating and deleting partitions, changing partition type codes, and so
136 on. Specific functions are:
137 b Save partition data to a backup file. You can back up your cur‐
140 rent in-memory partition table to a disk file using this option.
141 The resulting file is a binary file consisting of the protective
142 MBR, the main GPT header, the backup GPT header, and one copy of
143 the partition table, in that order. Note that the backup is of
144 the current in-memory data structures, so if you launch the pro‐
145 gram, make changes, and then use this option, the backup will
146 reflect your changes. Note also that the restore option is on
147 the recovery & transformation menu; the backup option is on the
148 main menu to encourage its use.
149 c Change the GPT name of a partition. This name is encoded as a
153 UTF-16 string, but proper entry and display of anything beyond
154 basic ASCII values requires suitable locale and font support.
155 For the most part, Linux ignores the partition name, but it may
156 be important in some OSes. GPT fdisk sets a default name based
157 on the partition type code. Note that the GPT partition name is
158 different from the filesystem name, which is encoded in the
159 filesystem's data structures.
160 d Delete a partition. This action deletes the entry from the par‐
163 tition table but does not disturb the data within the sectors
164 originally allocated to the partition on the disk. If a corre‐
165 sponding hybrid MBR partition exists, gdisk deletes it, as well,
166 and expands any adjacent 0xEE (EFI GPT) MBR protective partition
167 to fill the new free space.
168 i Show detailed partition information. The summary information
171 produced by the 'p' command necessarily omits many details, such
172 as the partition's unique GUID and the translation of gdisk's
173 internal partition type code to a plain type name. The 'i'
174 option displays this information for a single partition.
175 l Display a summary of partition types. GPT uses a GUID to iden‐
178 tify partition types for particular OSes and purposes. For ease
179 of data entry, gdisk compresses these into two-byte (four-digit
180 hexadecimal) values that are related to their equivalent MBR
181 codes. Specifically, the MBR code is multiplied by hexadecimal
182 0x0100. For instance, the code for Linux swap space in MBR is
183 0x82, and it's 0x8200 in gdisk. A one-to-one correspondence is
184 impossible, though. Most notably, the codes for all varieties of
185 FAT and NTFS partition correspond to a single GPT code (entered
186 as 0x0700 in sgdisk). Some OSes use a single MBR code but employ
187 many more codes in GPT. For these, gdisk adds code numbers
188 sequentially, such as 0xa500 for a FreeBSD disklabel, 0xa501 for
189 FreeBSD boot, 0xa502 for FreeBSD swap, and so on. Note that
190 these two-byte codes are unique to gdisk.
191 n Create a new partition. This command is modelled after the
194 equivalent fdisk option, although some differences exist. You
195 enter a partition number, starting sector, and an ending sector.
196 Both start and end sectors can be specified in absolute terms as
197 sector numbers or as positions measured in kibibytes (K),
198 mebibytes (M), gibibytes (G), tebibytes (T), or pebibytes (P);
199 for instance, 40M specifies a position 40MiB from the start of
200 the disk. You can specify locations relative to the start or end
201 of the specified default range by preceding the number by a '+'
202 or default start sector, or -200M to specify a point 200MiB
203 before the last available sector. Pressing the Enter key with no
204 input specifies the default value, which is the start of the
205 largest available block for the start sector and the end of the
206 same block for the end sector.
207 o Clear out all partition data. This includes GPT header data, all
210 partition definitions, and the protective MBR. The sector align‐
211 ment is reset to the default (2048 sectors, or 1MB).
212 p Display basic partition summary data. This includes partition
215 numbers, starting and ending sector numbers, partition sizes,
216 gdisk's partition types codes, and partition names. For addi‐
217 tional information, use the 'i' command.
218 q Quit from the program without saving your changes. Use this
221 option if you just wanted to view information or if you make a
222 mistake and want to back out of all your changes.
223 r Enter the recovery & transformation menu. This menu includes
226 emergency recovery options (to fix damaged GPT data structures)
227 and options to transform to or from other partitioning systems,
228 including creating hybrid MBRs.
229 s Sort partition entries. GPT partition numbers need not match the
232 order of partitions on the disk. If you want them to match, you
233 can use this option. Note that some partitioning utilities sort
234 partitions whenever they make changes. Such changes will be
235 reflected in your device filenames, so you may need to edit
236 /etc/fstab if you use this option.
237 t Change a single partition's type code. You enter the type code
240 using a two-byte hexadecimal number, as described earlier. You
241 may also enter a GUID directly, if you have one and gdisk
242 doesn't know it.
243 v Verify disk. This option checks for a variety of problems, such
246 as incorrect CRCs and mismatched main and backup data. This
247 option does not automatically correct most problems, though; for
248 that, you must use options on the recovery & transformation
249 menu. If no problems are found, this command displays a summary
250 of unallocated disk space.
251 w Write data. Use this command to save your changes.
254 x Enter the experts' menu. Using this option provides access to
257 features you can use to get into even more trouble than the main
258 menu allows.
259 ? Print the menu. Type this command (or any other unrecognized
261 command) to see a summary of available options.
262 The second gdisk menu is the recovery & transformation menu, which pro‐
265 vides access to data recovery options and features related to the
266 transformation of partitions between partitioning schemes (converting
267 BSD disklabels into GPT partitions or creating hybrid MBRs, for
268 instance). A few options on this menu duplicate functionality on the
269 main menu, for the sake of convenience. The options on this menu are:
270 b Rebuild GPT header from backup. You can use the backup GPT
273 header to rebuild the main GPT header with this option. It's
274 likely to be useful if your main GPT header was damaged or
275 destroyed (say, by sloppy use of dd).
276 c Load backup partition table. Ordinarily, gdisk uses only the
279 main partition table (although the backup's integrity is checked
280 when you launch the program). If the main partition table has
281 been damaged, you can use this option to load the backup from
282 disk and use it instead. Note that this will almost certainly
283 produce no or strange partition entries if you've just converted
284 an MBR disk to GPT format, since there will be no backup parti‐
285 tion table on disk.
286 d Use main GPT header and rebuild the backup. This option is
289 likely to be useful if the backup GPT header has been damaged or
290 destroyed.
291 e Load main partition table. This option reloads the main parti‐
294 tion table from disk. It's only likely to be useful if you've
295 tried to use the backup partition table (via 'c') but it's in
296 worse shape then the main partition table.
297 f Load MBR and build fresh GPT from it. Use this option if your
300 GPT is corrupt or conflicts with the MBR and you want to use the
301 MBR as the basis for a new set of GPT partitions.
302 g Convert GPT into MBR and exit. This option converts as many par‐
305 titions as possible into MBR form, destroys the GPT data struc‐
306 tures, saves the new MBR, and exits. Use this option if you've
307 tried GPT and find that MBR works better for you. Note that
308 this function generates up to four primary MBR partitions or
309 three primary partitions and as many logical partitions as can
310 be generated. Each logical partition requires at least one unal‐
311 located block immediately before its first block. Therefore, it
312 may be possible to convert a maximum of four partitions on disks
313 with tightly-packed partitions; however, if free space was
314 inserted between partitions when they were created, and if the
315 disk is under 2 TiB in size, it should be possible to convert
316 all the partitions to MBR form. See also the 'h' option.
317 h Create a hybrid MBR. This is an ugly workaround that enables
320 GPT-unaware OSes, or those that can't boot from a GPT disk, to
321 access up to three of the partitions on the disk by creating MBR
322 entries for them. Note that these hybrid MBR entries can easily
323 go out of sync with the GPT entries, particularly when
324 hybrid-unaware GPT utilities are used to edit the disk. Thus,
325 you may need to recreate the hybrid MBR if you use such tools.
326 Unlike the 'g' option, this option does not support converting
327 any partitions into MBR logical partitions.
328 i Show detailed partition information. This option is identical to
331 the 'i' option on the main menu.
332 l Load partition data from a backup file. This option is the
335 reverse of the 'b' option on the main menu. Note that restoring
336 partition data from anything but the original disk is not recom‐
337 mended.
338 m Return to the main menu. This option enables you to enter
341 main-menu commands.
342 o Print protective MBR data. You can see a summary of the protec‐
345 tive MBR's partitions with this option. This may enable you to
346 spot glaring problems or help identify the partitions in a
347 hybrid MBR.
348 p Print the partition table. This option is identical to the 'p'
351 option in the main menu.
352 q Quit without saving changes. This option is identical to the 'q'
355 option in the main menu.
356 t Transform BSD partitions into GPT partitions. This option works
359 on BSD disklabels held within GPT (or converted MBR) partitions.
360 Converted partitions' type codes are likely to need manual
361 adjustment. gdisk will attempt to convert BSD disklabels stored
362 on the main disk when launched, but this conversion is likely to
363 produce first and/or last partitions that are unusable. The many
364 BSD variants means that the probability of gdisk being unable to
365 convert a BSD disklabel is high compared to the likelihood of
366 problems with an MBR conversion.
367 v Verify disk. This option is identical to the 'v' option in the
370 main menu.
371 w Write table to disk and exit. This option is identical to the
374 'w' option in the main menu.
375 x Enter the experts' menu. This option is identical to the 'x'
378 option in the main menu.
379 ? Print the menu. This option (or any unrecognized entry) displays
382 a summary of the menu options.
383 The third gdisk menu is the experts' menu. This menu provides advanced
386 options that aren't closely related to recovery or transformation
387 between partitioning systems. Its options are:
388 a Set attributes. GPT provides a 64-bit attributes field that can
391 be used to set features for each partition. gdisk supports four
392 attributes: system partition, read-only, hidden, and do not
393 automount. You can set other attributes, but their numbers
394 aren't translated into anything useful. In practice, most OSes
395 seem to ignore these attributes.
396 c Change partition GUID. You can enter a custom unique GUID for a
399 partition using this option. (Note this refers to the GUID that
400 uniquely identifies a partition, not to its type code, which you
401 can change with the 't' main-menu option.) Ordinarily, gdisk
402 assigns this number randomly; however, you might want to adjust
403 the number manually if you've wound up with the same GUID on two
404 partitions because of buggy GUID assignments (hopefully not in
405 gdisk) or sheer incredible coincidence.
406 d Display the sector alignment value. See the description of the
409 'l' option for more details.
410 e Move backup GPT data structures to the end of the disk. Use this
413 command if you've added disks to a RAID array, thus creating a
414 virtual disk with space that follows the backup GPT data struc‐
415 tures. This command moves the backup GPT data structures to the
416 end of the disk, where they belong.
417 f Randomize the disk's GUID and all partitions' unique GUIDs (but
420 not their partition type code GUIDs). This function may be used
421 after cloning a disk with another utility in order to render all
422 GUIDs once again unique.
423 g Change disk GUID. Each disk has a unique GUID code, which gdisk
426 assigns randomly upon creation of the GPT data structures. You
427 can generate a fresh random GUID or enter one manually with this
428 option.
429 h Recompute CHS values in protective or hybrid MBR. This option
432 can sometimes help if a disk utility, OS, or BIOS doesn't like
433 the CHS values used by the partitions in the protective or
434 hybrid MBR. In particular, the GPT specification requires a CHS
435 value of 0xFFFFFF for over-8GiB partitions, but this value is
436 technically illegal by the usual standards. Some BIOSes hang if
437 they encounter this value. This option will recompute a more
438 normal CHS value -- 0xFEFFFF for over-8GiB partitions, enabling
439 these BIOSes to boot.
440 i Show detailed partition information. This option is identical to
443 the 'i' option on the main menu.
444 l Change the sector alignment value. Disks with more logical sec‐
447 tors per physical sectors (such as modern Advanced Format
448 drives), some RAID configurations, and many SSD devices, can
449 suffer performance problems if partitions are not aligned prop‐
450 erly for their internal data structures. On new disks, GPT fdisk
451 attempts to align partitions on 2048-sector (1MiB) boundaries by
452 default, which optimizes performance for all of these disk
453 types. On pre-partitioned disks, GPT fdisk attempts to identify
454 the alignment value used on that disk, but will set 8-sector
455 alignment on disks larger than 300 GB even if lesser alignment
456 values are detected. In either case, it can be changed by using
457 this option.
458 m Return to the main menu. This option enables you to enter
461 main-menu commands.
462 n Create a new protective MBR. Use this option if the current pro‐
465 tective MBR is damaged in a way that gdisk doesn't automatically
466 detect and correct, or if you want to convert a hybrid MBR into
467 a "pure" GPT with a conventional protective MBR.
468 o Print protective MBR data. You can see a summary of the protec‐
471 tive MBR's partitions with this option. This may enable you to
472 spot glaring problems or help identify the partitions in a
473 hybrid MBR.
474 p Print the partition table. This option is identical to the 'p'
477 option in the main menu.
478 q Quit without saving changes. This option is identical to the 'q'
481 option in the main menu.
482 r Enter the recovery & transformations menu. This option is iden‐
485 tical to the 'r' option on the main menu.
486 s Resize partition table. The default partition table size is 128
489 entries. Officially, sizes of less than 16KB (128 entries,
490 given the normal entry size) are unsupported by the GPT specifi‐
491 cation; however, in practice they seem to work, and can some‐
492 times be useful in converting MBR disks. Larger sizes also work
493 fine. OSes may impose their own limits on the number of parti‐
494 tions, though.
495 t Swap two partitions' entries in the partition table. One parti‐
498 tion may be empty. For instance, if partitions 1-4 are defined,
499 transposing 1 and 5 results in a table with partitions numbered
500 from 2-5. Transposing partitions in this way has no effect on
501 their disk space allocation; it only alters their order in the
502 partition table.
503 u Replicate the current device's partition table on another
506 device. You will be prompted to type the new device's filename.
507 After the write operation completes, you can continue editing
508 the original device's partition table. Note that the replicated
509 partition table is an exact copy, including all GUIDs; if the
510 device should have its own unique GUIDs, you should use the f
511 option on the new disk.
512 v Verify disk. This option is identical to the 'v' option in the
515 main menu.
516 z Zap (destroy) the GPT data structures and exit. Use this option
519 if you want to repartition a GPT disk using fdisk or some other
520 GPT-unaware program. You'll be given the choice of preserving
521 the existing MBR, in case it's a hybrid MBR with salvageable
522 partitions or if you've already created new MBR partitions and
523 want to erase the remnants of your GPT partitions. If you've
524 already created new MBR partitions, it's conceivable that this
525 option will damage the first and/or last MBR partitions! Such an
526 event is unlikely, but could occur if your new MBR partitions
527 overlap the old GPT data structures.
528 ? Print the menu. This option (or any unrecognized entry) displays
531 a summary of the menu options.
532 In many cases, you can press the Enter key to select a default option
535 when entering data. When only one option is possible, gdisk usually
536 bypasses the prompt entirely.
537
540 As of September 2011 (version 0.8.1), gdisk should be considered beta
541 software. Known bugs and limitations include:
542 * The program compiles correctly only on Linux, FreeBSD, Mac OS X,
545 and Windows. Linux versions for x86-64 (64-bit), x86 (32-bit),
546 and PowerPC (32-bit) have been tested, with the x86-64 version
547 having seen the most testing. Under FreeBSD, 32-bit (x86) and
548 64-bit (x86-64) versions have been tested. Only 32-bit versions
549 for Mac OS X and Windows have been tested by the author,
550 although I've heard of 64-bit versions being successfully com‐
551 piled.
552 * The FreeBSD version of the program can't write changes to the
555 partition table to a disk when existing partitions on that disk
556 are mounted. (The same problem exists with many other FreeBSD
557 utilities, such as gpt, fdisk, and dd.) This limitation can be
558 overcome by typing sysctl kern.geom.debugflags=16 at a shell
559 prompt.
560 * The fields used to display the start and end sector numbers for
563 partitions in the 'p' command are 14 characters wide. This
564 translates to a limitation of about 45 PiB. On larger disks, the
565 displayed columns will go out of alignment.
566 * In the Windows version, only ASCII characters are supported in
569 the partition name field. If an existing partition uses
570 non-ASCII UTF-16 characters, they're likely to be corrupted in
571 the 'i' and 'p' menu options' displays; however, they should be
572 preserved when loading and saving partitions. Binaries for
573 Linux, FreeBSD, and OS X support full UTF-16 partition names.
574 * The program can load only up to 128 partitions (4 primary parti‐
577 tions and 124 logical partitions) when converting from MBR for‐
578 mat. This limit can be raised by changing the #define
579 MAX_MBR_PARTS line in the basicmbr.h source code file and recom‐
580 piling; however, such a change will require using a
581 larger-than-normal partition table. (The limit of 128 partitions
582 was chosen because that number equals the 128 partitions sup‐
583 ported by the most common partition table size.)
584 * Converting from MBR format sometimes fails because of insuffi‐
587 cient space at the start or (more commonly) the end of the disk.
588 Resizing the partition table (using the 's' option in the
589 experts' menu) can sometimes overcome this problem; however, in
590 extreme cases it may be necessary to resize a partition using
591 GNU Parted or a similar tool prior to conversion with gdisk.
592 * MBR conversions work only if the disk has correct LBA partition
595 descriptors. These descriptors should be present on any disk
596 over 8 GiB in size or on smaller disks partitioned with any but
597 very ancient software.
598 * BSD disklabel support can create first and/or last partitions
601 that overlap with the GPT data structures. This can sometimes be
602 compensated by adjusting the partition table size, but in
603 extreme cases the affected partition(s) may need to be deleted.
604 * Because of the highly variable nature of BSD disklabel struc‐
607 tures, conversions from this form may be unreliable -- parti‐
608 tions may be dropped, converted in a way that creates overlaps
609 with other partitions, or converted with incorrect start or end
610 values. Use this feature with caution!
611 * Booting after converting an MBR or BSD disklabel disk is likely
614 to be disrupted. Sometimes re-installing a boot loader will fix
615 the problem, but other times you may need to switch boot load‐
616 ers. Except on EFI-based platforms, Windows through at least
617 Windows 7 doesn't support booting from GPT disks. Creating a
618 hybrid MBR (using the 'h' option on the recovery & transforma‐
619 tion menu) or abandoning GPT in favor of MBR may be your only
620 options in this case.
621
624 Primary author: Roderick W. Smith (rodsmith@rodsbooks.com)
625 Contributors:
627 * Yves Blusseau (1otnwmz02@sneakemail.com)
629 * David Hubbard (david.c.hubbard@gmail.com)
631 * Justin Maggard (justin.maggard@netgear.com)
633 * Dwight Schauer (dschauer@ti.com)
635 * Florian Zumbiehl (florz@florz.de)
637
641 cfdisk (8), cgdisk (8), fdisk (8), mkfs (8), parted (8), sfdisk (8)
642 sgdisk (8) fixparts (8)
643 http://en.wikipedia.org/wiki/GUID_Partition_Table
645 http://developer.apple.com/technotes/tn2006/tn2166.html
647 http://www.rodsbooks.com/gdisk/
649
652 The gdisk command is part of the GPT fdisk package and is available
653 from Rod Smith.
654Roderick W. Smith 0.8.1 GDISK(8)