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

6       sgdisk  - Command-line GUID partition table (GPT) manipulator for Linux
7       and Unix
8

SYNOPSIS

10       sgdisk [ options ] device
11
12

DESCRIPTION

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
23       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
30       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
37       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
45       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
51       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
56       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
72       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
78       When creating a fresh partition table, certain considerations may be in
79       order:
80
81
82       *      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
86
87       *      Boot disks for EFI-based systems require an EFI System Partition
88              (gdisk internal code 0xEF00) formatted as FAT-32. I  recommended
89              making  this  partition  550  MiB. (Smaller ESPs are common, but
90              some EFIs have flaky FAT drivers that necessitate a larger  par‐
91              tition  for  reliable  operation.) Boot-related files are stored
92              here. (Note that GNU Parted identifies such partitions as having
93              the "boot flag" set.)
94
95
96       *      Some boot loaders for BIOS-based systems make use of a BIOS Boot
97              Partition (gdisk internal code 0xEF02), in which  the  secondary
98              boot  loader  is  stored,  possibly  without  the  benefit  of a
99              filesystem. (GRUB2 may optionally use such  a  partition.)  This
100              partition  can  typically be quite small (roughly 32 to 200 KiB,
101              although 1 MiB is more common in practice), but you should  con‐
102              sult your boot loader documentation for details.
103
104
105       *      If  Windows  is to boot from a GPT disk, a partition of type Mi‐
106              crosoft Reserved (sgdisk internal code 0x0C01)  is  recommended.
107              This  partition  should  be about 128 MiB in size. It ordinarily
108              follows the EFI System Partition and  immediately  precedes  the
109              Windows  data  partitions. (Note that GNU Parted creates all FAT
110              partitions as this type,  which  actually  makes  the  partition
111              unusable for normal file storage in both Windows and Mac OS X.)
112
113
114       *      Some  OSes' GPT utilities create some blank space (typically 128
115              MiB) after each partition. The intent is to enable  future  disk
116              utilities  to use this space. Such free space is not required of
117              GPT disks, but creating it may help in future disk maintenance.
118
119

OPTIONS

121       Some options take no arguments, others take one argument  (typically  a
122       partition number), and others take compound arguments with colon delim‐
123       itation. For instance, -n (--new) takes a partition number, a  starting
124       sector   number,   and  an  ending  sector  number,  as  in  sgdisk  -n
125       2:2000:50000 /dev/sdc, which  creates  a  new  partition,  numbered  2,
126       starting at sector 2000 an ending at sector 50,000, on /dev/sdc.
127
128       Unrelated options may be combined; however, some such combinations will
129       be nonsense (such as deleting a partition and then  changing  its  GUID
130       type  code).   sgdisk  interprets options in the order in which they're
131       entered, so effects can vary depending on order. For  instance,  sgdisk
132       -s  -d 2 sorts the partition table entries and then deletes partition 2
133       from the newly-sorted list; but sgdisk -d 2  -s  deletes  the  original
134       partition 2 and then sorts the modified partition table.
135
136       Error checking and opportunities to correct mistakes in sgdisk are min‐
137       imal. Although the program endeavors to keep the  GPT  data  structures
138       legal,  it  does  not  prompt  for  verification  before performing its
139       actions. Unless you require a command-line-driven program,  you  should
140       use  the interactive gdisk instead of sgdisk, since gdisk allows you to
141       quit without saving your changes, should you make a mistake.
142
143       Although sgdisk is based on the  same  partition-manipulation  code  as
144       gdisk,  sgdisk  implements fewer features than its interactive sibling.
145       Options available in sgdisk are:
146
147
148       -a, --set-alignment=value
149              Set the sector alignment multiple. GPT fdisk aligns the start of
150              partitions  to  sectors  that are multiples of this value, which
151              defaults to 1 MiB (2048  on  disks  with  512-byte  sectors)  on
152              freshly  formatted  disks.  This alignment value is necessary to
153              obtain optimum performance with Western Digital Advanced  Format
154              and  similar  drives  with  larger  physical than logical sector
155              sizes, with some types of RAID arrays, and with SSD devices.
156
157
158       -A,        --attributes=list|[partnum:show|or|nand|xor|=|set|clear|tog‐
159       gle|get[:bitnum|hexbitmask]]
160              View  or  set  partition  attributes.  Use  list  to see defined
161              (known) attribute values. Omit the partition  number  (and  even
162              the  device filename) when using this option. The others require
163              a partition number. The show and get options  show  the  current
164              attribute  settings  (all  attributes  or  for a particular bit,
165              respectively). The or, nand, xor,  =,  set,  clear,  and  toggle
166              options  enable  you to change the attribute bit value. The set,
167              clear, toggle, and get options work on a bit number; the  others
168              work  on  a  hexadecimal  bit  mask. For example, type sgdisk -A
169              4:set:2 /dev/sdc  to  set  the  bit  2  attribute  (legacy  BIOS
170              bootable) on partition 4 on /dev/sdc.
171
172
173       -b, --backup=file
174              Save  partition data to a backup file. You can back up your cur‐
175              rent in-memory partition table to a disk file using this option.
176              The resulting file is a binary file consisting of the protective
177              MBR, the main GPT header, the backup GPT header, and one copy of
178              the  partition  table, in that order. Note that the backup is of
179              the current in-memory data structures, so if you launch the pro‐
180              gram,  make  changes,  and then use this option, the backup will
181              reflect your changes. If the GPT data  structures  are  damaged,
182              the  backup  may  not  accurately  reflect  the  damaged  state;
183              instead, they will reflect GPT fdisk's first-pass interpretation
184              of the GPT.
185
186
187       -c, --change-name=partnum:name
188              Change  the  GPT  name of a partition. This name is encoded as a
189              UTF-16 string, but proper entry and display of  anything  beyond
190              basic  ASCII  values  requires suitable locale and font support.
191              For the most part, Linux ignores the partition name, but it  may
192              be  important  in  some  OSes.  If  you  want to set a name that
193              includes a space, enclose it in quotation marks, as in sgdisk -c
194              1:"Sample  Name" /dev/sdb. Note that the GPT name of a partition
195              is distinct from the filesystem name, which is  encoded  in  the
196              filesystem's data structures.
197
198
199       -C, --recompute-chs
200              Recompute  CHS  values  in protective or hybrid MBR. This option
201              can sometimes help if a disk utility, OS, or BIOS  doesn't  like
202              the  CHS  values  used  by  the  partitions in the protective or
203              hybrid MBR. In particular, the GPT specification requires a  CHS
204              value  of  0xFFFFFF  for over-8GiB partitions, but this value is
205              technically illegal by the usual standards. Some BIOSes hang  if
206              they  encounter  this  value.  This option will recompute a more
207              normal CHS value -- 0xFEFFFF for over-8GiB partitions,  enabling
208              these BIOSes to boot.
209
210
211       -d, --delete=partnum
212              Delete  a partition. This action deletes the entry from the par‐
213              tition table but does not disturb the data  within  the  sectors
214              originally  allocated  to the partition on the disk. If a corre‐
215              sponding hybrid MBR partition exists, gdisk deletes it, as well,
216              and expands any adjacent 0xEE (EFI GPT) MBR protective partition
217              to fill the new free space.
218
219
220       -D, --display-alignment
221              Display current sector alignment value. Partitions will be  cre‐
222              ated  on  multiples of the sector value reported by this option.
223              You can change the alignment value with the -a option.
224
225
226       -e, --move-second-header
227              Move backup GPT data structures to the end of the disk. Use this
228              option  if  you've  added disks to a RAID array, thus creating a
229              virtual disk with space that follows the backup GPT data  struc‐
230              tures.  This command moves the backup GPT data structures to the
231              end of the disk, where they belong.
232
233
234       -E, --end-of-largest
235              Displays the sector number of the end of the  largest  available
236              block  of sectors on the disk. A script may store this value and
237              pass it back as part of -n's option to create a partition. If no
238              unallocated  sectors  are  available,  this function returns the
239              value 0.
240
241
242       -f, --first-in-largest
243              Displays the sector number of the start of the largest available
244              block  of sectors on the disk. A script may store this value and
245              pass it back as part of -n's option to create a partition. If no
246              unallocated  sectors  are  available,  this function returns the
247              value 0. Note that this parameter is blind to  partition  align‐
248              ment;  when  you  actually  create  a partition, its start point
249              might be changed from this value.
250
251
252       -F, --first-aligned-in-largest
253              Similar to -f (--first-in-largest), except  returns  the  sector
254              number  with  the current alignment correction applied. Use this
255              function if you need to compute the actual partition start point
256              rather  than a theoretical start point or the actual start point
257              if you set the alignment value to 1.
258
259
260       -g, --mbrtogpt
261              Convert an MBR or BSD disklabel disk to a GPT disk. As a  safety
262              measure,  use of this option is required on MBR or BSD disklabel
263              disks if you intend to save your changes, in  order  to  prevent
264              accidentally damaging such disks.
265
266
267       -G, --randomize-guids
268              Randomize  the disk's GUID and all partitions' unique GUIDs (but
269              not their partition type code GUIDs). This function may be  used
270              after  cloning  a  disk  in order to render all GUIDs once again
271              unique.
272
273
274       -h, --hybrid
275              Create a hybrid MBR. This option takes from one to three  parti‐
276              tion numbers, separated by colons, as arguments. You may option‐
277              ally specify a final partition "EE" to indicate that the EFI GPT
278              (type  0xEE)  should  be  placed last in the table, otherwise it
279              will be placed first, followed by the partition(s) you  specify.
280              Their  type  codes are based on the GPT fdisk type codes divided
281              by 0x0100, which is usually correct for Windows  partitions.  If
282              the  active/bootable  flag  should  be  set,  you  must do so in
283              another program, such as fdisk. The gdisk program  offers  addi‐
284              tional hybrid MBR creation options.
285
286
287       -i, --info=partnum
288              Show  detailed  partition  information.  The summary information
289              produced by the -p command necessarily omits many details,  such
290              as  the  partition's unique GUID and the translation of sgdisk's
291              internal partition type code to a plain type name. The -i option
292              displays this information for a single partition.
293
294
295       -j, --adjust-main-table=sector
296              Adjust  the  location of the main partition table. This value is
297              normally 2, but it may need to be increased in some cases,  such
298              as  when  a system-on-chip (SoC) is hard-coded to read boot code
299              from sector 2. I recommend against adjusting this  value  unless
300              doing so is absolutely necessary.
301
302
303       -l, --load-backup=file
304              Load  partition  data  from  a  backup  file. This option is the
305              reverse of the -b option. Note  that  restoring  partition  data
306              from  anything  but  the  original disk is not recommended. This
307              option will work even if the disk's original partition table  is
308              bad;  however,  most other options on the same command line will
309              be ignored.
310
311
312       -L, --list-types
313              Display a summary of partition types. GPT uses a GUID  to  iden‐
314              tify  partition types for particular OSes and purposes. For ease
315              of data entry, sgdisk compresses these into two-byte (four-digit
316              hexadecimal)  values  that  are  related to their equivalent MBR
317              codes. Specifically, the MBR code is multiplied  by  hexadecimal
318              0x0100.  For  instance,  the code for Linux swap space in MBR is
319              0x82, and it's 0x8200 in gdisk. A one-to-one  correspondence  is
320              impossible, though. Most notably, the codes for all varieties of
321              FAT and NTFS partition correspond to a single GPT code  (entered
322              as 0x0700 in sgdisk). Some OSes use a single MBR code but employ
323              many more codes in GPT. For  these,  sgdisk  adds  code  numbers
324              sequentially, such as 0xa500 for a FreeBSD disklabel, 0xa501 for
325              FreeBSD boot, 0xa502 for FreeBSD swap,  and  so  on.  Note  that
326              these two-byte codes are unique to gdisk and sgdisk. This option
327              does not require you to specify a valid disk device filename.
328
329
330       -m, --gpttombr
331              Convert disk from GPT to MBR form. This option takes from one to
332              four partition numbers, separated by colons, as arguments. Their
333              type codes are based on the GPT  fdisk  type  codes  divided  by
334              0x0100.  If  the active/bootable flag should be set, you must do
335              so in another program, such as fdisk.  The gdisk program  offers
336              additional MBR conversion options. It is not possible to convert
337              more than four partitions from GPT to MBR  form  or  to  convert
338              partitions  that  start  above  the 2TiB mark or that are larger
339              than 2TiB.
340
341
342       -n, --new=partnum:start:end
343              Create a new partition. You enter a partition  number,  starting
344              sector,  and an ending sector. Both start and end sectors can be
345              specified in absolute terms as sector numbers  or  as  positions
346              measured   in  kibibytes  (K),  mebibytes  (M),  gibibytes  (G),
347              tebibytes (T), or pebibytes (P); for instance, 40M  specifies  a
348              position 40MiB from the start of the disk. You can specify loca‐
349              tions relative to the start or  end  of  the  specified  default
350              range  by preceding the number by a '+' or '-' symbol, as in +2G
351              to specify a point 2GiB after the default start sector, or -200M
352              to  specify  a  point 200MiB before the last available sector. A
353              start or end value of 0 specifies the default  value,  which  is
354              the  start  of  the largest available block for the start sector
355              and the end of the same block for  the  end  sector.  A  partnum
356              value  of 0 causes the program to use the first available parti‐
357              tion number. Subsequent uses of the -A, -c, -t, and  -u  options
358              may also use 0 to refer to the same partition.
359
360
361       -N, --largest-new=num
362              Create a new partition that fills the largest available block of
363              space on the disk. You can use the -a  (--set-alignment)  option
364              to adjust the alignment, if desired. A num value of 0 causes the
365              program to use the first available partition number.
366
367
368       -o, --clear
369              Clear out all partition data. This includes GPT header data, all
370              partition  definitions,  and  the protective MBR. Note that this
371              operation will, like most other operations, fail  on  a  damaged
372              disk.  If  you want to prepare a disk you know to be damaged for
373              GPT use, you should first wipe it with -Z and then partition  it
374              normally. This option will work even if the disk's original par‐
375              tition table is bad; however, most other  options  on  the  same
376              command line will be ignored.
377
378
379       -O, --print-mbr
380              Display  basic  MBR partition summary data. This includes parti‐
381              tion numbers, starting  and  ending  sector  numbers,  partition
382              sizes,  MBR  partition  types  codes,  and partition names. This
383              option is useful mainly for diagnosing partition table problems,
384              particularly on disks with hybrid MBRs.
385
386
387       -p, --print
388              Display  basic  GPT partition summary data. This includes parti‐
389              tion numbers, starting  and  ending  sector  numbers,  partition
390              sizes,  sgdisk's partition types codes, and partition names. For
391              additional information, use the -i (--info) option.
392
393
394       -P, --pretend
395              Pretend to make specified changes. In-memory GPT data structures
396              are  altered  according to other parameters, but changes are not
397              written to disk.
398
399
400       -r, --transpose
401              Swap two partitions' entries in the partition table. One or both
402              partitions  may be empty, although swapping two empty partitions
403              is pointless. For  instance,  if  partitions  1-4  are  defined,
404              transposing  1 and 5 results in a table with partitions numbered
405              from 2-5. Transposing partitions in this way has  no  effect  on
406              their  disk  space allocation; it only alters their order in the
407              partition table.
408
409
410       -R, --replicate=second_device_filename
411              Replicate the main device's partition  table  on  the  specified
412              second  device.   Note that the replicated partition table is an
413              exact copy, including all GUIDs; if the device should  have  its
414              own unique GUIDs, you should use the -G option on the new disk.
415
416
417       -s, --sort
418              Sort partition entries. GPT partition numbers need not match the
419              order of partitions on the disk. If you want them to match,  you
420              can use this option.  Note that some partitioning utilities sort
421              partitions whenever they make  changes.  Such  changes  will  be
422              reflected  in  your  device  filenames,  so you may need to edit
423              /etc/fstab if you use this option.
424
425
426       -t, --typecode=partnum:{hexcode|GUID}
427              Change a single partition's type code. You enter the  type  code
428              using  either  a  two-byte hexadecimal number, as described ear‐
429              lier,   or   a   fully-specified    GUID    value,    such    as
430              EBD0A0A2-B9E5-4433-87C0-68B6B72699C7.
431
432
433       -T, --transform-bsd=partnum
434              Transform  BSD partitions into GPT partitions. This option works
435              on BSD disklabels held within GPT (or converted MBR) partitions.
436              Converted  partitions'  type  codes  are  likely  to need manual
437              adjustment. sgdisk will attempt to convert BSD disklabels stored
438              on the main disk when launched, but this conversion is likely to
439              produce first and/or last partitions that are unusable. The many
440              BSD  variants  means that the probability of sgdisk being unable
441              to convert a BSD disklabel is high compared to the likelihood of
442              problems with an MBR conversion.
443
444
445       -u, --partition-guid=partnum:guid
446              Set  the  partition unique GUID for an individual partition. The
447              GUID may be a complete GUID or 'R' to set a random GUID.
448
449
450       -U, --disk-guid=guid
451              Set the GUID for the disk. The GUID may be a  complete  GUID  or
452              'R' to set a random GUID.
453
454
455       --usage
456              Print a brief summary of available options.
457
458
459       -v, --verify
460              Verify  disk. This option checks for a variety of problems, such
461              as incorrect CRCs and mismatched  main  and  backup  data.  This
462              option does not automatically correct most problems, though; for
463              that, you must use options  on  the  recovery  &  transformation
464              menu.  If no problems are found, this command displays a summary
465              of unallocated disk space. This option will  work  even  if  the
466              disk's  original  partition  table  is  bad; however, most other
467              options on the same command line will be ignored.
468
469
470       -V, --version
471              Display program version information. This  option  may  be  used
472              without specifying a device filename.
473
474
475       -z, --zap
476              Zap  (destroy)  the  GPT data structures and then exit. Use this
477              option if you want to repartition a GPT disk using fdisk or some
478              other  GPT-unaware  program.  This  option destroys only the GPT
479              data structures; it leaves the MBR intact. This makes it  useful
480              for  wiping out GPT data structures after a disk has been repar‐
481              titioned for MBR using a GPT-unaware utility; however, there's a
482              risk  that  it will damage boot loaders or even the start of the
483              first or end of the last MBR partition. If you use it on a valid
484              GPT  disk,  the  MBR  will be left with an inappropriate EFI GPT
485              (0xEE) partition definition, which you can delete using  another
486              utility.
487
488
489       -Z, --zap-all
490              Zap  (destroy)  the  GPT  and MBR data structures and then exit.
491              This option works much like -z, but as it wipes the MBR as  well
492              as the GPT, it's more suitable if you want to repartition a disk
493              after using this option, and  completely  unsuitable  if  you've
494              already repartitioned the disk.
495
496
497       -?, --help
498              Print a summary of options.
499
500

RETURN VALUES

502       sgdisk returns various values depending on its success or failure:
503
504
505       0      Normal program execution
506
507
508       1      Too few arguments
509
510
511       2      An error occurred while reading the partition table
512
513
514       3      Non-GPT disk detected and no -g option, but operation requires a
515              write action
516
517
518       4      An error prevented saving changes
519
520
521       5      An error occurred while reading  standard  input  (should  never
522              occur with sgdisk, but may with gdisk)
523
524
525       8      Disk replication operation (-R) failed
526
527

BUGS

529       Known bugs and limitations include:
530
531
532       *      The  program  compiles correctly only on Linux, FreeBSD, and Mac
533              OS X. Linux versions for x86-64 (64-bit), x86 (32-bit), and Pow‐
534              erPC  (32-bit)  have been tested, with the x86-64 version having
535              seen the most testing.
536
537
538       *      The FreeBSD version of the program can't write  changes  to  the
539              partition  table to a disk when existing partitions on that disk
540              are mounted. (The same problem exists with  many  other  FreeBSD
541              utilities,  such  as gpt, fdisk, and dd.) This limitation can be
542              overcome by typing sysctl  kern.geom.debugflags=16  at  a  shell
543              prompt.
544
545
546       *      The  fields used to display the start and end sector numbers for
547              partitions in the -p option are 14 characters wide. This  trans‐
548              lates to a limitation of about 45 PiB. On larger disks, the dis‐
549              played columns will go out of alignment.
550
551
552       *      The program can load only up to 128 partitions (4 primary parti‐
553              tions  and 124 logical partitions) when converting from MBR for‐
554              mat.  This  limit  can  be  raised  by  changing   the   #define
555              MAX_MBR_PARTS line in the basicmbr.h source code file and recom‐
556              piling;  however,  such  a   change   will   require   using   a
557              larger-than-normal partition table. (The limit of 128 partitions
558              was chosen because that number equals the  128  partitions  sup‐
559              ported by the most common partition table size.)
560
561
562       *      Converting  from  MBR format sometimes fails because of insuffi‐
563              cient space at the start or (more commonly) the end of the disk.
564              Resizing  the  partition  table  (using  the  's'  option in the
565              experts' menu) can sometimes overcome this problem; however,  in
566              extreme  cases  it  may be necessary to resize a partition using
567              GNU Parted or a similar tool prior to conversion with gdisk.
568
569
570       *      MBR conversions work only if the disk has correct LBA  partition
571              descriptors.  These  descriptors  should  be present on any disk
572              over 8 GiB in size or on smaller disks partitioned with any  but
573              very ancient software.
574
575
576       *      BSD  disklabel  support  can create first and/or last partitions
577              that overlap with the GPT data structures. This can sometimes be
578              compensated  by  adjusting  the  partition  table  size,  but in
579              extreme cases the affected partition(s) may need to be deleted.
580
581
582       *      Because of the highly variable nature of  BSD  disklabel  struc‐
583              tures,  conversions  from  this form may be unreliable -- parti‐
584              tions may be dropped, converted in a way that  creates  overlaps
585              with  other partitions, or converted with incorrect start or end
586              values. Use this feature with caution!
587
588
589       *      Booting after converting an MBR or BSD disklabel disk is  likely
590              to  be disrupted. Sometimes re-installing a boot loader will fix
591              the problem, but other times you may need to switch  boot  load‐
592              ers.  Except  on  EFI-based  platforms, Windows through at least
593              Windows 7 RC doesn't support booting from GPT disks. Creating  a
594              hybrid  MBR  (using the 'h' option on the recovery & transforma‐
595              tion menu) or abandoning GPT in favor of MBR may  be  your  only
596              options in this case.
597
598

AUTHORS

600       Primary author: Roderick W. Smith (rodsmith@rodsbooks.com)
601
602       Contributors:
603
604       * Yves Blusseau (1otnwmz02@sneakemail.com)
605
606       * David Hubbard (david.c.hubbard@gmail.com)
607
608       * Justin Maggard (justin.maggard@netgear.com)
609
610       * Dwight Schauer (dschauer@gmail.com)
611
612       * Florian Zumbiehl (florz@florz.de)
613
614
615

SEE ALSO

617       cfdisk(8),   cgdisk(8),   fdisk(8),   gdisk(8),   mkfs(8),   parted(8),
618       sfdisk(8), fixparts(8).
619
620       http://en.wikipedia.org/wiki/GUID_Partition_Table
621
622       http://developer.apple.com/technotes/tn2006/tn2166.html
623
624       http://www.rodsbooks.com/gdisk/
625
626

AVAILABILITY

628       The sgdisk command is part of the GPT fdisk package  and  is  available
629       from Rod Smith.
630
631
632
633Roderick W. Smith                    1.0.5                           SGDISK(8)
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