1GDISK(8)                       GPT fdisk Manual                       GDISK(8)
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NAME

6       gdisk - Interactive GUID partition table (GPT) manipulator
7

SYNOPSIS

9       gdisk [ -l ] device
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11

DESCRIPTION

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
21       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
33       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
41       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
49       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
57       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
62       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
78       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
83       When creating a fresh partition table, certain considerations may be in
84       order:
85
86
87       *      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
91
92       *      Boot disks for EFI-based systems require an EFI System Partition
93              (gdisk  internal code 0xEF00) formatted as FAT-32. I recommended
94              making this partition 550 MiB. (Smaller  ESPs  are  common,  but
95              some  EFIs have flaky FAT drivers that necessitate a larger par‐
96              tition for reliable operation.) Boot-related  files  are  stored
97              here. (Note that GNU Parted identifies such partitions as having
98              the "boot flag" set.)
99
100
101       *      Some boot loaders for BIOS-based systems make use of a BIOS Boot
102              Partition  (gdisk  internal code 0xEF02), in which the secondary
103              boot loader  is  stored,  possibly  without  the  benefit  of  a
104              filesystem.  (GRUB2  may  optionally use such a partition.) This
105              partition can typically be quite small (roughly 32 to  200  KiB,
106              although  1 MiB is more common in practice), but you should con‐
107              sult your boot loader documentation for details.
108
109
110       *      If Windows is to boot from a GPT disk, a partition of  type  Mi‐
111              crosoft  Reserved  (gdisk  internal code 0x0C01) is recommended.
112              This partition should be about 128 MiB in  size.  It  ordinarily
113              follows  the  EFI  System Partition and immediately precedes the
114              Windows data partitions. (Note that old versions of  GNU  Parted
115              create all FAT partitions as this type, which actually makes the
116              partition unusable for normal file storage in both  Windows  and
117              Mac OS X.)
118
119
120       *      Some  OSes' GPT utilities create some blank space (typically 128
121              MiB) after each partition. The intent is to enable  future  disk
122              utilities  to use this space. Such free space is not required of
123              GPT disks, but creating it may help in future disk  maintenance.
124              You  can  use  GPT fdisk's relative partition positioning option
125              (specifying the starting sector as  '+128M',  for  instance)  to
126              simplify creating such gaps.
127
128

OPTIONS

130       -l     List  the  partition  table  for  the  specified device and then
131              exits.
132
133       Most interactions with  gdisk  occur  with  its  interactive  text-mode
134       menus.  Three menus exist: the main menu, the recovery & transformation
135       menu, and the experts' menu. The main menu provides the functions  that
136       are  most  likely  to be useful for typical partitioning tasks, such as
137       creating and deleting partitions, changing partition type codes, and so
138       on. Specific functions are:
139
140
141       b      Save  partition data to a backup file. You can back up your cur‐
142              rent in-memory partition table to a disk file using this option.
143              The resulting file is a binary file consisting of the protective
144              MBR, the main GPT header, the backup GPT header, and one copy of
145              the  partition  table, in that order. Note that the backup is of
146              the current in-memory data structures, so if you launch the pro‐
147              gram,  make  changes,  and then use this option, the backup will
148              reflect your changes. Note also that the restore  option  is  on
149              the  recovery & transformation menu; the backup option is on the
150              main menu to encourage its use.
151
152
153
154       c      Change the GPT name of a partition. This name is  encoded  as  a
155              UTF-16  string,  but proper entry and display of anything beyond
156              basic ASCII values requires suitable locale  and  font  support.
157              For  the most part, Linux ignores the partition name, but it may
158              be important in some OSes. GPT fdisk sets a default  name  based
159              on  the partition type code. Note that the GPT partition name is
160              different from the filesystem name,  which  is  encoded  in  the
161              filesystem's data structures.
162
163
164       d      Delete  a partition. This action deletes the entry from the par‐
165              tition table but does not disturb the data  within  the  sectors
166              originally  allocated  to the partition on the disk. If a corre‐
167              sponding hybrid MBR partition exists, gdisk deletes it, as well,
168              and expands any adjacent 0xEE (EFI GPT) MBR protective partition
169              to fill the new free space.
170
171
172       i      Show detailed partition  information.  The  summary  information
173              produced by the 'p' command necessarily omits many details, such
174              as the partition's unique GUID and the  translation  of  gdisk's
175              internal  partition  type  code  to  a  plain type name. The 'i'
176              option displays this information for a single partition.
177
178
179       l      Display a summary of partition types. GPT uses a GUID  to  iden‐
180              tify  partition types for particular OSes and purposes. For ease
181              of data entry, gdisk compresses these into two-byte  (four-digit
182              hexadecimal)  values  that  are  related to their equivalent MBR
183              codes. Specifically, the MBR code is multiplied  by  hexadecimal
184              0x0100.  For  instance,  the code for Linux swap space in MBR is
185              0x82, and it's 0x8200 in gdisk. A one-to-one  correspondence  is
186              impossible, though. Most notably, the codes for all varieties of
187              FAT and NTFS partition correspond to a single GPT code  (entered
188              as  0x0700 in gdisk). Some OSes use a single MBR code but employ
189              many more codes in GPT.  For  these,  gdisk  adds  code  numbers
190              sequentially, such as 0xa500 for a FreeBSD disklabel, 0xa501 for
191              FreeBSD boot, 0xa502 for FreeBSD swap,  and  so  on.  Note  that
192              these two-byte codes are unique to gdisk. The type code list may
193              optionally be filtered by a search string; for instance,  enter‐
194              ing Linux shows only partition type codes with descriptions that
195              include the string Linux. This search is  performed  case-sensi‐
196              tively.
197
198
199       n      Create a new partition. This command is modeled after the equiv‐
200              alent fdisk option, although some differences exist. You enter a
201              partition  number,  starting  sector, and an ending sector. Both
202              start and end sectors can be specified in absolute terms as sec‐
203              tor numbers or as positions measured in kibibytes (K), mebibytes
204              (M),  gibibytes  (G),  tebibytes  (T),  or  pebibytes  (P);  for
205              instance,  40M  specifies a position 40MiB from the start of the
206              disk. You can specify locations relative to the start or end  of
207              the  specified default range by preceding the number by a '+' or
208              '-' symbol, as in +2G to specify a point 2GiB after the  default
209              start sector, or -200M to specify a point 200MiB before the last
210              available sector. Pressing the Enter key with no input specifies
211              the  default  value, which is the start of the largest available
212              block for the start sector and the end of the same block for the
213              end sector.
214
215
216       o      Clear out all partition data. This includes GPT header data, all
217              partition definitions, and the protective MBR. The sector align‐
218              ment  is  reset  to  the default (1MB, or 2048 sectors on a disk
219              with 512-byte sectors).
220
221
222       p      Display basic partition summary data.  This  includes  partition
223              numbers,  starting  and  ending sector numbers, partition sizes,
224              gdisk's partition types codes, and partition  names.  For  addi‐
225              tional information, use the 'i' command.
226
227
228       q      Quit  from  the  program  without saving your changes.  Use this
229              option if you just wanted to view information or if you  make  a
230              mistake and want to back out of all your changes.
231
232
233       r      Enter  the  recovery  &  transformation menu. This menu includes
234              emergency recovery options (to fix damaged GPT data  structures)
235              and  options to transform to or from other partitioning systems,
236              including creating hybrid MBRs.
237
238
239       s      Sort partition entries. GPT partition numbers need not match the
240              order  of partitions on the disk. If you want them to match, you
241              can use this option.  Note that some partitioning utilities sort
242              partitions  whenever  they  make  changes.  Such changes will be
243              reflected in your device filenames, so  you  may  need  to  edit
244              /etc/fstab if you use this option.
245
246
247       t      Change  a  single partition's type code. You enter the type code
248              using a two-byte hexadecimal number, as described  earlier.  You
249              may  also  enter  a  GUID  directly,  if  you have one and gdisk
250              doesn't know it.
251
252
253       v      Verify disk. This option checks for a variety of problems,  such
254              as  incorrect  CRCs  and  mismatched  main and backup data. This
255              option does not automatically correct most problems, though; for
256              that,  you  must  use  options  on the recovery & transformation
257              menu. If no problems are found, this command displays a  summary
258              of unallocated disk space.
259
260
261       w      Write data. Use this command to save your changes.
262
263
264       x      Enter  the  experts'  menu. Using this option provides access to
265              features you can use to get into even more trouble than the main
266              menu allows.
267
268       ?      Print  the  menu.  Type  this command (or any other unrecognized
269              command) to see a summary of available options.
270
271
272       The second gdisk menu is the recovery & transformation menu, which pro‐
273       vides  access  to  data  recovery  options  and features related to the
274       transformation of partitions between partitioning  schemes  (converting
275       BSD  disklabels  into  GPT  partitions  or  creating  hybrid  MBRs, for
276       instance).  A few options on this menu duplicate functionality  on  the
277       main menu, for the sake of convenience. The options on this menu are:
278
279
280       b      Rebuild  GPT  header  from  backup.  You  can use the backup GPT
281              header to rebuild the main GPT header  with  this  option.  It's
282              likely  to  be  useful  if  your  main GPT header was damaged or
283              destroyed (say, by sloppy use of dd).
284
285
286       c      Load backup partition table. Ordinarily,  gdisk  uses  only  the
287              main partition table (although the backup's integrity is checked
288              when you launch the program). If the main  partition  table  has
289              been  damaged,  you  can use this option to load the backup from
290              disk and use it instead. Note that this  will  almost  certainly
291              produce no or strange partition entries if you've just converted
292              an MBR disk to GPT format, since there will be no backup  parti‐
293              tion table on disk.
294
295
296       d      Use  main  GPT  header  and  rebuild  the backup. This option is
297              likely to be useful if the backup GPT header has been damaged or
298              destroyed.
299
300
301       e      Load  main  partition table. This option reloads the main parti‐
302              tion table from disk. It's only likely to be  useful  if  you've
303              tried  to  use  the backup partition table (via 'c') but it's in
304              worse shape then the main partition table.
305
306
307       f      Load MBR and build fresh GPT from it. Use this  option  if  your
308              GPT is corrupt or conflicts with the MBR and you want to use the
309              MBR as the basis for a new set of GPT partitions.
310
311
312       g      Convert GPT into MBR and exit. This option converts as many par‐
313              titions  as possible into MBR form, destroys the GPT data struc‐
314              tures, saves the new MBR, and exits.  Use this option if  you've
315              tried  GPT  and  find  that MBR works better for you.  Note that
316              this function generates up to four  primary  MBR  partitions  or
317              three  primary  partitions and as many logical partitions as can
318              be generated. Each logical partition requires at least one unal‐
319              located  block immediately before its first block. Therefore, it
320              may be possible to convert a maximum of four partitions on disks
321              with  tightly-packed  partitions;  however,  if  free  space was
322              inserted between partitions when they were created, and  if  the
323              disk  is  under  2 TiB in size, it should be possible to convert
324              all the partitions to MBR form.  See also the 'h' option.
325
326
327       h      Create a hybrid MBR. This is an  ugly  workaround  that  enables
328              GPT-unaware  OSes,  or those that can't boot from a GPT disk, to
329              access up to three of the partitions on the disk by creating MBR
330              entries  for them. Note that these hybrid MBR entries can easily
331              go  out  of  sync  with  the  GPT  entries,  particularly   when
332              hybrid-unaware  GPT  utilities are used to edit the disk.  Thus,
333              you may need to re-create the hybrid MBR if you use such  tools.
334              Unlike  the  'g' option, this option does not support converting
335              any partitions into MBR logical partitions.
336
337
338       i      Show detailed partition information. This option is identical to
339              the 'i' option on the main menu.
340
341
342       l      Load  partition  data  from  a  backup  file. This option is the
343              reverse of the 'b' option on the main menu. Note that  restoring
344              partition data from anything but the original disk is not recom‐
345              mended.
346
347
348       m      Return to the main  menu.  This  option  enables  you  to  enter
349              main-menu commands.
350
351
352       o      Print  protective MBR data. You can see a summary of the protec‐
353              tive MBR's partitions with this option. This may enable  you  to
354              spot  glaring  problems  or  help  identify  the partitions in a
355              hybrid MBR.
356
357
358       p      Print the partition table. This option is identical to  the  'p'
359              option in the main menu.
360
361
362       q      Quit without saving changes. This option is identical to the 'q'
363              option in the main menu.
364
365
366       t      Transform BSD partitions into GPT partitions. This option  works
367              on BSD disklabels held within GPT (or converted MBR) partitions.
368              Converted partitions' type  codes  are  likely  to  need  manual
369              adjustment.  gdisk will attempt to convert BSD disklabels stored
370              on the main disk when launched, but this conversion is likely to
371              produce first and/or last partitions that are unusable. The many
372              BSD variants means that the probability of gdisk being unable to
373              convert  a  BSD  disklabel is high compared to the likelihood of
374              problems with an MBR conversion.
375
376
377       v      Verify disk. This option is identical to the 'v' option  in  the
378              main menu.
379
380
381       w      Write  table  to  disk and exit. This option is identical to the
382              'w' option in the main menu.
383
384
385       x      Enter the experts' menu. This option is  identical  to  the  'x'
386              option in the main menu.
387
388
389       ?      Print the menu. This option (or any unrecognized entry) displays
390              a summary of the menu options.
391
392
393       The third gdisk menu is the experts' menu. This menu provides  advanced
394       options  that  aren't  closely  related  to  recovery or transformation
395       between partitioning systems. Its options are:
396
397
398       a      Set attributes. GPT provides a 64-bit attributes field that  can
399              be  used to set features for each partition. gdisk supports four
400              attributes: system partition,  read-only,  hidden,  and  do  not
401              automount.  You  can  set  other  attributes,  but their numbers
402              aren't translated into anything useful. In practice,  most  OSes
403              seem to ignore these attributes.
404
405
406       c      Change  partition GUID. You can enter a custom unique GUID for a
407              partition using this option. (Note this refers to the GUID  that
408              uniquely identifies a partition, not to its type code, which you
409              can change with the 't'  main-menu  option.)  Ordinarily,  gdisk
410              assigns  this number randomly; however, you might want to adjust
411              the number manually if you've wound up with the same GUID on two
412              partitions  because  of buggy GUID assignments (hopefully not in
413              gdisk) or sheer incredible coincidence.
414
415
416       d      Display the sector alignment value. See the description  of  the
417              'l' option for more details.
418
419
420       e      Move backup GPT data structures to the end of the disk. Use this
421              command if you've added disks to a RAID array, thus  creating  a
422              virtual  disk with space that follows the backup GPT data struc‐
423              tures. This command moves the backup GPT data structures to  the
424              end of the disk, where they belong.
425
426
427       f      Randomize  the disk's GUID and all partitions' unique GUIDs (but
428              not their partition type code GUIDs). This function may be  used
429              after cloning a disk with another utility in order to render all
430              GUIDs once again unique.
431
432
433       g      Change disk GUID. Each disk has a unique GUID code, which  gdisk
434              assigns  randomly  upon creation of the GPT data structures. You
435              can generate a fresh random GUID or enter one manually with this
436              option.
437
438
439       h      Recompute  CHS  values  in protective or hybrid MBR. This option
440              can sometimes help if a disk utility, OS, or BIOS  doesn't  like
441              the  CHS  values  used  by  the  partitions in the protective or
442              hybrid MBR. In particular, the GPT specification requires a  CHS
443              value  of  0xFFFFFF  for over-8GiB partitions, but this value is
444              technically illegal by the usual standards. Some BIOSes hang  if
445              they  encounter  this  value.  This option will recompute a more
446              normal CHS value -- 0xFEFFFF for over-8GiB partitions,  enabling
447              these BIOSes to boot.
448
449
450       i      Show detailed partition information. This option is identical to
451              the 'i' option on the main menu.
452
453
454       j      Adjust the location of the main partition table. This  value  is
455              normally  2, but it may need to be increased in some cases, such
456              as when a system-on-chip (SoC) is hard-coded to read  boot  code
457              from  sector  2. I recommend against adjusting this value unless
458              doing so is absolutely necessary.
459
460
461       l      Change the sector alignment value. Disks with more logical  sec‐
462              tors  per  physical  sectors  (such  as  modern  Advanced Format
463              drives), some RAID configurations, and  many  SSD  devices,  can
464              suffer  performance problems if partitions are not aligned prop‐
465              erly for their internal data structures. On new disks, GPT fdisk
466              attempts to align partitions on 1MiB boundaries (2048-sectors on
467              disks with 512-byte sectors) by default, which optimizes perfor‐
468              mance for all of these disk types. On pre-partitioned disks, GPT
469              fdisk attempts to identify the  alignment  value  used  on  that
470              disk,  but  will set 8-sector alignment on disks larger than 300
471              GB even if lesser alignment values are detected. In either case,
472              it can be changed by using this option.
473
474
475       m      Return  to  the  main  menu.  This  option  enables you to enter
476              main-menu commands.
477
478
479       n      Create a new protective MBR. Use this option if the current pro‐
480              tective MBR is damaged in a way that gdisk doesn't automatically
481              detect and correct, or if you want to convert a hybrid MBR  into
482              a "pure" GPT with a conventional protective MBR.
483
484
485       o      Print  protective MBR data. You can see a summary of the protec‐
486              tive MBR's partitions with this option. This may enable  you  to
487              spot  glaring  problems  or  help  identify  the partitions in a
488              hybrid MBR.
489
490
491       p      Print the partition table. This option is identical to  the  'p'
492              option in the main menu.
493
494
495       q      Quit without saving changes. This option is identical to the 'q'
496              option in the main menu.
497
498
499       r      Enter the recovery & transformations menu. This option is  iden‐
500              tical to the 'r' option on the main menu.
501
502
503       s      Resize  partition table. The default partition table size is 128
504              entries.  Officially, sizes of  less  than  16KB  (128  entries,
505              given the normal entry size) are unsupported by the GPT specifi‐
506              cation; however, in practice they seem to work,  and  can  some‐
507              times  be useful in converting MBR disks. Larger sizes also work
508              fine. OSes may impose their own limits on the number  of  parti‐
509              tions, though.
510
511
512       t      Swap  two partitions' entries in the partition table. One parti‐
513              tion may be empty. For instance, if partitions 1-4 are  defined,
514              transposing  1 and 5 results in a table with partitions numbered
515              from 2-5. Transposing partitions in this way has  no  effect  on
516              their  disk  space allocation; it only alters their order in the
517              partition table.
518
519
520       u      Replicate  the  current  device's  partition  table  on  another
521              device.  You will be prompted to type the new device's filename.
522              After the write operation completes, you  can  continue  editing
523              the original device's partition table.  Note that the replicated
524              partition table is an exact copy, including all  GUIDs;  if  the
525              device  should  have  its own unique GUIDs, you should use the f
526              option on the new disk.
527
528
529       v      Verify disk. This option is identical to the 'v' option  in  the
530              main menu.
531
532
533       z      Zap  (destroy) the GPT data structures and exit. Use this option
534              if you want to repartition a GPT disk using fdisk or some  other
535              GPT-unaware  program.   You'll be given the choice of preserving
536              the existing MBR, in case it's a  hybrid  MBR  with  salvageable
537              partitions  or  if you've already created new MBR partitions and
538              want to erase the remnants of your  GPT  partitions.  If  you've
539              already  created  new MBR partitions, it's conceivable that this
540              option will damage the first and/or last MBR partitions! Such an
541              event  is  unlikely,  but could occur if your new MBR partitions
542              overlap the old GPT data structures.
543
544
545       ?      Print the menu. This option (or any unrecognized entry) displays
546              a summary of the menu options.
547
548
549       In  many  cases, you can press the Enter key to select a default option
550       when entering data. When only one option  is  possible,  gdisk  usually
551       bypasses the prompt entirely.
552
553

BUGS

555       Known bugs and limitations include:
556
557
558       *      The program compiles correctly only on Linux, FreeBSD, Mac OS X,
559              and Windows.  Linux versions for x86-64 (64-bit), x86  (32-bit),
560              and  PowerPC  (32-bit) have been tested, with the x86-64 version
561              having seen the most testing. Under FreeBSD,  32-bit  (x86)  and
562              64-bit  (x86-64) versions have been tested. Only 32-bit versions
563              for Mac OS X  and  Windows  have  been  tested  by  the  author,
564              although  I've  heard of 64-bit versions being successfully com‐
565              piled.
566
567
568       *      The FreeBSD version of the program can't write  changes  to  the
569              partition  table to a disk when existing partitions on that disk
570              are mounted. (The same problem exists with  many  other  FreeBSD
571              utilities,  such  as gpt, fdisk, and dd.) This limitation can be
572              overcome by typing sysctl  kern.geom.debugflags=16  at  a  shell
573              prompt.
574
575
576       *      The  fields used to display the start and end sector numbers for
577              partitions in the 'p'  command  are  14  characters  wide.  This
578              translates to a limitation of about 45 PiB. On larger disks, the
579              displayed columns will go out of alignment.
580
581
582       *      In the Windows version, only ASCII characters are  supported  in
583              the   partition  name  field.  If  an  existing  partition  uses
584              non-ASCII UTF-16 characters, they're likely to be  corrupted  in
585              the  'i' and 'p' menu options' displays; however, they should be
586              preserved when  loading  and  saving  partitions.  Binaries  for
587              Linux, FreeBSD, and OS X support full UTF-16 partition names.
588
589
590       *      The program can load only up to 128 partitions (4 primary parti‐
591              tions and 124 logical partitions) when converting from MBR  for‐
592              mat.   This   limit  can  be  raised  by  changing  the  #define
593              MAX_MBR_PARTS line in the basicmbr.h source code file and recom‐
594              piling;   however,   such   a   change   will  require  using  a
595              larger-than-normal partition table. (The limit of 128 partitions
596              was  chosen  because  that number equals the 128 partitions sup‐
597              ported by the most common partition table size.)
598
599
600       *      Converting from MBR format sometimes fails because  of  insuffi‐
601              cient space at the start or (more commonly) the end of the disk.
602              Resizing the partition  table  (using  the  's'  option  in  the
603              experts'  menu) can sometimes overcome this problem; however, in
604              extreme cases it may be necessary to resize  a  partition  using
605              GNU Parted or a similar tool prior to conversion with gdisk.
606
607
608       *      MBR  conversions work only if the disk has correct LBA partition
609              descriptors. These descriptors should be  present  on  any  disk
610              over  8 GiB in size or on smaller disks partitioned with any but
611              very ancient software.
612
613
614       *      BSD disklabel support can create first  and/or  last  partitions
615              that overlap with the GPT data structures. This can sometimes be
616              compensated by  adjusting  the  partition  table  size,  but  in
617              extreme cases the affected partition(s) may need to be deleted.
618
619
620       *      Because  of  the  highly variable nature of BSD disklabel struc‐
621              tures, conversions from this form may be  unreliable  --  parti‐
622              tions  may  be dropped, converted in a way that creates overlaps
623              with other partitions, or converted with incorrect start or  end
624              values. Use this feature with caution!
625
626
627       *      Booting  after converting an MBR or BSD disklabel disk is likely
628              to be disrupted. Sometimes re-installing a boot loader will  fix
629              the  problem,  but other times you may need to switch boot load‐
630              ers. Except on EFI-based platforms,  Windows  through  at  least
631              Windows  7  doesn't  support  booting from GPT disks. Creating a
632              hybrid MBR (using the 'h' option on the recovery  &  transforma‐
633              tion  menu)  or  abandoning GPT in favor of MBR may be your only
634              options in this case.
635
636

AUTHORS

638       Primary author: Roderick W. Smith (rodsmith@rodsbooks.com)
639
640       Contributors:
641
642       * Yves Blusseau (1otnwmz02@sneakemail.com)
643
644       * David Hubbard (david.c.hubbard@gmail.com)
645
646       * Justin Maggard (justin.maggard@netgear.com)
647
648       * Dwight Schauer (dschauer@gmail.com)
649
650       * Florian Zumbiehl (florz@florz.de)
651
652
653

SEE ALSO

655       cfdisk (8), cgdisk (8), fdisk (8), mkfs (8),  parted  (8),  sfdisk  (8)
656       sgdisk (8) fixparts (8)
657
658       http://en.wikipedia.org/wiki/GUID_Partition_Table
659
660       http://developer.apple.com/technotes/tn2006/tn2166.html
661
662       http://www.rodsbooks.com/gdisk/
663
664

AVAILABILITY

666       The  gdisk  command  is  part of the GPT fdisk package and is available
667       from Rod Smith.
668
669
670
671Roderick W. Smith                    1.0.4                            GDISK(8)
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