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       gdisk - GUID partition table (GPT) manipulator for Linux and Unix


       gdisk [ -l ] device


       GPT  fdisk  (aka gdisk) is a text-mode menu-driven program for creation
       and manipulation of partition tables. It will automatically convert  an
       old-style  Master  Boot  Record  (MBR) partition table or BSD disklabel
       stored without an MBR carrier partition to the  newer  Globally  Unique
       Identifier  (GUID)  Partition  Table  (GPT) format, or will load a GUID
       partition table. When used with the -l command-line option, the program
       displays the current partition table and then exits.

       GPT  fdisk  operates  mainly  on  the GPT headers and partition tables;
       however, it  can  and  will  generate  a  fresh  protective  MBR,  when
       required.  (Any  boot  loader  code  in  the protective MBR will not be
       disturbed.) If you’ve created an unusual  protective  MBR,  such  as  a
       hybrid  MBR  created  by  gptsync  or  gdisk’s  own hybrid MBR creation
       feature, this should not be disturbed by most  ordinary  actions.  Some
       advanced   data   recovery   options  require  you  to  understand  the
       distinctions between the main and backup data, as well as  between  the
       GPT  headers  and the partition tables. For information on MBR vs. GPT,
       as well as GPT  terminology  and  structure,  see  the  extended  gdisk
       documentation  at or consult Wikipedia.

       The gdisk program employs a user interface similar to that  of  Linux’s
       fdisk, but gdisk modifies GPT partitions. It also has the capability of
       transforming MBR partitions or BSD disklabels into GPT partitions. Like
       the original fdisk program, gdisk does not modify disk structures until
       you explicitly write them to disk, so if you make a  mistake,  you  can
       exit from the program with the ’q’ option to save your partitions.

       Ordinarily,  gdisk  operates  on disk device files, such as /dev/sda or
       /dev/hda under Linux,  /dev/disk0  under  Mac  OS  X,  or  /dev/ad0  or
       /dev/da0  under  FreeBSD.  The  program  can also operate on disk image
       files, which can be either copies of whole disks  (made  with  dd,  for
       instance)  or raw disk images used by emulators such as QEMU or VMWare.
       Note that only raw disk images are  supported;  gdisk  cannot  work  on
       compressed or other advanced disk image formats.

       The  MBR partitioning system uses a combination of cylinder/head/sector
       (CHS) addressing and logical block  addressing  (LBA).  The  former  is
       klunky  and limiting. GPT drops CHS addressing and uses 64-bit LBA mode
       exclusively. Thus, GPT data structures, and  therefore  gdisk,  do  not
       need  to  deal  with  CHS  geometries and all the problems they create.
       Users of fdisk will note that gdisk lacks the options  and  limitations
       associated with CHS geometries.

       For best results, you should use an OS-specific partition table program
       whenever possible. For example, you should make  Mac  OS  X  partitions
       with  the  Mac  OS X Disk Utility program and Linux partitions with the
       Linux gdisk or GNU Parted program.

       Upon start, gdisk attempts to identify the partition type in use on the
       disk.  If  it finds valid GPT data, gdisk will use it. If gdisk finds a
       valid MBR or BSD disklabel but no GPT data, it will attempt to  convert
       the  MBR or disklabel into GPT form. (BSD disklabels are likely to have
       unusable first and/or final partitions because they  overlap  with  the
       GPT  data structures, though.) GPT fdisk can identify, but not use data
       in, Apple Partition Map (APM) disks,  which  are  used  on  680x0-  and
       PowerPC-based  Macintoshes.  Upon  exiting  with  the ’w’ option, gdisk
       replaces the MBR or disklabel with a GPT. This  action  is  potentially
       dangerous!  Your system may become unbootable, and partition type codes
       may become corrupted if the disk uses  unrecognized  type  codes.  Boot
       problems  are  particularly  likely  if  you’re  multi-booting with any
       GPT-unaware OS. If you mistakenly launch gdisk on an MBR disk, you  can
       safely  exit  the  program  without making any changes by using the ’q’

       The MBR-to-GPT conversion will leave at least one gap in the  partition
       numbering  if  the original MBR used logical partitions. These gaps are
       harmless, but you can eliminate them by using the ’s’  option,  if  you
       like.  (Doing this may require you to update your /etc/fstab file.)

       When creating a fresh partition table, certain considerations may be in

       *      For data (non-boot) disks, and for boot disks used on BIOS-based
              computers  with  GRUB  as  the  boot  loader,  partitions may be
              created in whatever order and in whatever sizes are desired.

       *      Boot disks for EFI-based systems require an EFI System Partition
              (gdisk   internal   code   0xEF00)  formatted  as  FAT-32.   The
              recommended size of this partition is between 100 and  200  MiB.
              Boot-related  files  are  stored  here.  (Note  that  GNU Parted
              identifies such partitions as having the "boot flag" set.)

       *      Some boot loaders for BIOS-based systems make use of a BIOS Boot
              Partition  (gdisk  internal code 0xEF02), in which the secondary
              boot loader  is  stored,  possibly  without  the  benefit  of  a
              filesystem. This partition can typically be quite small (roughly
              32 to  200  KiB),  but  you  should  consult  your  boot  loader
              documentation for details.

       *      If  Windows  is  to  boot  from  a GPT disk, a partition of type
              Microsoft Reserved (gdisk internal code 0x0C01) is  recommended.
              This  partition  should  be about 128 MiB in size. It ordinarily
              follows the EFI System Partition and  immediately  precedes  the
              Windows  data  partitions. (Note that GNU Parted creates all FAT
              partitions as this type,  which  actually  makes  the  partition
              unusable  for normal file storage in both Windows and Mac OS X.)

       *      Some OSes’ GPT utilities create some blank space (typically  128
              MiB)  after  each partition. The intent is to enable future disk
              utilities to use this space. Such free space is not required  of
              GPT  disks, but creating it may help in future disk maintenance.
              You can use GPT fdisk’s relative  partition  positioning  option
              (specifying  the  starting  sector  as ’+128M’, for instance) to
              simplify creating such gaps.


       -l     List the partition tables for the  specified  devices  and  then

       Most  interactions  with  gdisk  occur  with  its interactive text-mode
       menus. Three menus exist: the main menu, the recovery &  transformation
       menu,  and the experts’ menu. The main menu provides the functions that
       are most likely to be useful for typical partitioning  tasks,  such  as
       creating and deleting partitions, changing partition type codes, and so
       on. Specific functions are:

       b      Save partition data to a backup  file.  You  can  back  up  your
              current  in-memory  partition  table  to  a disk file using this
              option. The resulting file is a binary file  consisting  of  the
              protective  MBR, the main GPT header, the backup GPT header, and
              one copy of the partition table, in that order.  Note  that  the
              backup  is  of  the current in-memory data structures, so if you
              launch the program, make changes, and then use this option,  the
              backup  will  reflect  your  changes. Note also that the restore
              option is on the recovery  &  transformation  menu;  the  backup
              option is on the main menu to encourage its use.

       c      Change  the  GPT  name of a partition. This name is encoded as a
              UTF-16 string, but  gdisk  supports  only  ASCII  characters  as
              names.  For the most part, Linux ignores the partition name, but
              it may be important in some OSes. GPT fdisk sets a default  name
              based on the partition type code.

       d      Delete  a  partition.  This  action  deletes  the entry from the
              partition table but does not disturb the data within the sectors
              originally  allocated  to  the  partition  on  the  disk.  If  a
              corresponding hybrid MBR partition exists, gdisk deletes it,  as
              well,  and  expands  any  adjacent 0xEE (EFI GPT) MBR protective
              partition to fill the new free space.

       i      Show detailed partition  information.  The  summary  information
              produced by the ’p’ command necessarily omits many details, such
              as the partition’s unique GUID and the  translation  of  gdisk’s
              internal  partition  type  code  to  a  plain type name. The ’i’
              option displays this information for a single partition.

       l      Display a summary  of  partition  types.  GPT  uses  a  GUID  to
              identify  partition  types for particular OSes and purposes. For
              ease  of  data  entry,  gdisk  compresses  these  into  two-byte
              (four-digit  hexadecimal)  values  that  are  related  to  their
              equivalent MBR codes. Specifically, the MBR code  is  multiplied
              by  hexadecimal  0x0100.  For  instance, the code for Linux swap
              space in MBR is 0x82, and it’s 0x8200 in  gdisk.   A  one-to-one
              correspondence  is  impossible,  though. Most notably, many DOS,
              Windows, and Linux data partition codes correspond to  a  single
              GPT  code  (entered  as 0x0700 in gdisk). Some OSes use a single
              MBR code but employ many more codes in  GPT.  For  these,  gdisk
              adds  code  numbers  sequentially,  such as 0xa500 for a FreeBSD
              disklabel, 0xa501 for FreeBSD boot, 0xa502 for FreeBSD swap, and
              so on. Note that these two-byte codes are unique to gdisk.

       n      Create  a  new  partition.  This  command  is modelled after the
              equivalent fdisk option, although some  differences  exist.  You
              enter a partition number, starting sector, and an ending sector.
              Both start and end sectors can be specified in absolute terms as
              sector  numbers  or  as  positions  measured  in  kilobytes (K),
              megabytes (M), gigabytes (G), or terabytes  (T);  for  instance,
              40M  specifies  a position 40MiB from the start of the disk. You
              can specify locations relative  to  the  start  or  end  of  the
              specified  range by preceding the number by a ’+’ or ’-’ symbol,
              as in +2G to specify a point  2GiB  after  the  first  available
              sector,  or  -200M  to  specify  a  point 200MiB before the last
              available sector. Pressing the Enter key with no input specifies
              the  default  value, which is the start of the largest available
              block for the start sector and the last available block for  the
              end sector.

       o      Clear out all partition data. This includes GPT header data, all
              partition definitions, and the protective MBR.

       p      Display basic partition summary data.  This  includes  partition
              numbers,  starting  and  ending sector numbers, partition sizes,
              gdisk’s  partition  types  codes,  and  partition   names.   For
              additional information, use the ’i’ command.

       q      Quit  from  the  program  without saving your changes.  Use this
              option if you just wanted to view information or if you  make  a
              mistake and want to back out of all your changes.

       r      Enter  the  recovery  &  transformation menu. This menu includes
              emergency recovery options (to fix damaged GPT data  structures)
              and  options to transform to or from other partitioning systems,
              including creating hybrid MBRs.

       s      Sort partition entries. GPT partition numbers need not match the
              order  of partitions on the disk. If you want them to match, you
              can use this option.  Note that some partitioning utilities sort
              partitions  whenever  they  make  changes.  Such changes will be
              reflected in your device filenames, so  you  may  need  to  edit
              /etc/fstab if you use this option.

       t      Change  a  single partition’s type code. You enter the type code
              using a two-byte hexadecimal number, as described  earlier.  You
              may  also  enter  a  GUID  directly,  if  you have one and gdisk
              doesn’t know it.

       v      Verify disk. This option checks for a variety of problems,  such
              as  incorrect  CRCs  and  mismatched  main and backup data. This
              option does not automatically correct most problems, though; for
              that,  you  must  use  options  on the recovery & transformation
              menu. If no problems are found, this command displays a  summary
              of unallocated disk space.

       w      Write data. Use this command to save your changes.

       x      Enter  the  experts’  menu. Using this option provides access to
              features you can use to get into even more trouble than the main
              menu allows.

       ?      Print  the  menu.  Type  this command (or any other unrecognized
              command) to see a summary of available options.

       The second gdisk menu is the  recovery  &  transformation  menu,  which
       provides  access  to  data recovery options and features related to the
       transformation of partitions between partitioning  schemes  (converting
       BSD  disklabels  into  GPT  partitions  or  creating  hybrid  MBRs, for
       instance).  A few options on this menu duplicate functionality  on  the
       main menu, for the sake of convenience. The options on this menu are:

       b      Rebuild  GPT  header  from  backup.  You  can use the backup GPT
              header to rebuild the main GPT header  with  this  option.  It’s
              likely  to  be  useful  if  your  main GPT header was damaged or
              destroyed (say, by sloppy use of dd).

       c      Load backup partition table. Ordinarily,  gdisk  uses  only  the
              main partition table (although the backup’s integrity is checked
              when you launch the program). If the main  partition  table  has
              been  damaged,  you  can use this option to load the backup from
              disk and use it instead. Note that this  will  almost  certainly
              produce no or strange partition entries if you’ve just converted
              an MBR disk to  GPT  format,  since  there  will  be  no  backup
              partition table on disk.

       d      Use  main  GPT  header  and  rebuild  the backup. This option is
              likely to be useful if the backup GPT header has been damaged or

       e      Load   main  partition  table.  This  option  reloads  the  main
              partition table from disk. It’s only  likely  to  be  useful  if
              you’ve  tried  to  use  the backup partition table (via ’c’) but
              it’s in worse shape then the main partition table.

       f      Load MBR and build fresh GPT from it. Use this  option  if  your
              GPT is corrupt or conflicts with the MBR and you want to use the
              MBR as the basis for a new set of GPT partitions.

       g      Convert GPT into MBR and exit. This option converts up  to  four
              GPT  partitions into MBR form, destroys the GPT data structures,
              saves the new MBR, and exits.  Use this option if  you’ve  tried
              GPT  and  find  that  MBR  works better for you.  Note that this
              function generates up to four primary MBR partitions; it  cannot
              generate  logical  partitions,  and  so it cannot transform more
              than four partitions. If four or fewer partitions exist, and  if
              they  can  be  represented  in  the  32-bit MBR LBA scheme, this
              function converts them all. If more than four partitions  exist,
              you’ll  be  asked  to select which ones to convert. See also the
              ’h’ option.

       h      Create a hybrid MBR. This is an  ugly  workaround  that  enables
              GPT-unaware  OSes,  or those that can’t boot from a GPT disk, to
              access up to three of the partitions on the disk by creating MBR
              entries  for them. Note that these hybrid MBR entries can easily
              go  out  of  sync  with  the  GPT  entries,  particularly   when
              hybrid-unaware  GPT  utilities are used to edit the disk.  Thus,
              you may need to recreate the hybrid MBR if you use such tools.

       i      Show detailed partition information. This option is identical to
              the ’i’ option on the main menu.

       l      Load  partition  data  from  a  backup  file. This option is the
              reverse of the ’b’ option on the main menu. Note that  restoring
              partition  data  from  anything  but  the  original  disk is not

       m      Return to the main  menu.  This  option  enables  you  to  enter
              main-menu commands.

       o      Print  protective  MBR  data.  You  can  see  a  summary  of the
              protective MBR’s partitions with this option.  This  may  enable
              you  to spot glaring problems or help identify the partitions in
              a hybrid MBR.

       p      Print the partition table. This option is identical to  the  ’p’
              option in the main menu.

       q      Quit without saving changes. This option is identical to the ’q’
              option in the main menu.

       t      Transform BSD partitions into GPT partitions. This option  works
              on BSD disklabels held within GPT (or converted MBR) partitions.
              Converted partitions’ type  codes  are  likely  to  need  manual
              adjustment.  gdisk will attempt to convert BSD disklabels stored
              on the main disk when launched, but this conversion is likely to
              produce first and/or last partitions that are unusable. The many
              BSD variants means that the probability of gdisk being unable to
              convert  a  BSD  disklabel is high compared to the likelihood of
              problems with an MBR conversion.

       v      Verify disk. This option is identical to the ’v’ option  in  the
              main menu.

       w      Write  table  to  disk and exit. This option is identical to the
              ’w’ option in the main menu.

       x      Enter the experts’ menu. This option is  identical  to  the  ’x’
              option in the main menu.

       ?      Print the menu. This option (or any unrecognized entry) displays
              a summary of the menu options.

       The third gdisk menu is the experts’ menu. This menu provides  advanced
       options  that  aren’t  closely  related  to  recovery or transformation
       between partitioning systems. Its options are:

       a      Set attributes. GPT provides a 64-bit attributes field that  can
              be  used to set features for each partition. gdisk supports four
              attributes: system partition,  read-only,  hidden,  and  do  not
              automount.  You  can  set  other  attributes,  but their numbers
              aren’t translated into anything useful. In practice,  most  OSes
              seem to ignore these attributes.

       c      Change  partition GUID. You can enter a custom unique GUID for a
              partition using this option. (Note this refers to the GUID  that
              uniquely identifies a partition, not to its type code, which you
              can change with the ’t’  main-menu  option.)  Ordinarily,  gdisk
              assigns  this number randomly; however, you might want to adjust
              the number manually if you’ve wound up with the same GUID on two
              partitions  because  of buggy GUID assignments (hopefully not in
              gdisk) or sheer incredible coincidence.

       e      Move backup GPT data structures to the end of the disk. Use this
              command  if  you’ve added disks to a RAID array, thus creating a
              virtual disk  with  space  that  follows  the  backup  GPT  data
              structures. This command moves the backup GPT data structures to
              the end of the disk, where they belong.

       g      Change disk GUID. Each disk has a unique GUID code, which  gdisk
              assigns  randomly  upon creation of the GPT data structures. You
              can generate a fresh random GUID or enter one manually with this

       i      Show detailed partition information. This option is identical to
              the ’i’ option on the main menu.

       m      Return to the main  menu.  This  option  enables  you  to  enter
              main-menu commands.

       n      Create  a  new  protective  MBR.  Use this option if the current
              protective  MBR  is  damaged  in  a  way  that   gdisk   doesn’t
              automatically  detect  and  correct, or if you want to convert a
              hybrid MBR into a "pure" GPT with a conventional protective MBR.

       o      Print  protective  MBR  data.  You  can  see  a  summary  of the
              protective MBR’s partitions with this option.  This  may  enable
              you  to spot glaring problems or help identify the partitions in
              a hybrid MBR.

       p      Print the partition table. This option is identical to  the  ’p’
              option in the main menu.

       q      Quit without saving changes. This option is identical to the ’q’
              option in the main menu.

       r      Enter the  recovery  &  transformations  menu.  This  option  is
              identical to the ’r’ option on the main menu.

       s      Resize  partition table. The default partition table size is 128
              entries.  Officially, sizes of  less  than  16KB  (128  entries,
              given  the  normal  entry  size)  are  unsupported  by  the  GPT
              specification; however, in practice they seem to work,  and  can
              sometimes  be  useful in converting MBR disks. Larger sizes also
              work fine. OSes may impose their own limits  on  the  number  of
              partitions, though.

       v      Verify  disk.  This option is identical to the ’v’ option in the
              main menu.

       z      Zap (destroy) the GPT data structures and exit. Use this  option
              if  you want to repartition a GPT disk using fdisk or some other
              GPT-unaware program.  You’ll be given the choice  of  preserving
              the  existing  MBR,  in  case it’s a hybrid MBR with salvageable
              partitions or if you’ve already created new MBR  partitions  and
              want  to  erase  the  remnants of your GPT partitions. If youve
              already created new MBR partitions, its conceivable  that  this
              option will damage the first and/or last MBR partitions! Such an
              event is unlikely, but could occur if your  new  MBR  partitions
              overlap the old GPT data structures.

       ?      Print the menu. This option (or any unrecognized entry) displays
              a summary of the menu options.

       In many cases, you can press the Enter key to select a  default  option
       when  entering  data.  When  only one option is possible, gdisk usually
       bypasses the prompt entirely.


       As of November 2009 (version 0.5.1), gdisk should  be  considered  beta
       software. Known bugs and limitations include:

       *      The  program  compiles correctly only on Linux, FreeBSD, and Mac
              OS X. Linux versions for  x86-64  (64-bit),  x86  (32-bit),  and
              PowerPC  (32-bit)  have  been  tested,  with  the x86-64 version
              having seen the most testing. The Mac OS  X  support  was  added
              with  version  0.3.1  and  has  not  been  as thoroughly tested.
              FreeBSD support was added with version 0.4.0 and has  seen  even
              less testing.

       *      The  FreeBSD  version  of the program can’t write changes to the
              partition table to a disk when existing partitions on that  disk
              are  mounted.  (The  same problem exists with many other FreeBSD
              utilities, such as gpt, fdisk, and dd.)

       *      The fields used to display the start and end sector numbers  for
              partitions  in  the  ’p’  command  are  14 characters wide. This
              translates to a limitation of about 45 PiB. On larger disks, the
              displayed columns will go out of alignment.

       *      Only ASCII characters are supported in the partition name field.
              If an  existing  partition  uses  non-ASCII  UTF-16  characters,
              they’re  likely to be corrupted in the ’i’ and ’p’ menu options’
              displays; however, they should be  preserved  when  loading  and
              saving partitions.

       *      The  program  can  load  only  up  to  128 partitions (4 primary
              partitions and 124 logical partitions) when converting from  MBR
              format.  This  limit  can  be  raised  by  changing  the #define
              MAX_MBR_PARTS  line  in  the  mbr.h   source   code   file   and
              recompiling;  however,  such  a  change  will  require  using  a
              larger-than-normal partition table. (The limit of 128 partitions
              was  chosen  because  that  number  equals  the  128  partitions
              supported by the most common partition table size.)

       *      Converting  from  MBR  format   sometimes   fails   because   of
              insufficient  space  at  the start or (more commonly) the end of
              the disk. Resizing the partition table (using the ’s’ option  in
              the experts’ menu) can sometimes overcome this problem; however,
              in extreme cases it may be necessary to resize a partition using
              GNU Parted or a similar tool prior to conversion with gdisk.

       *      MBR  conversions work only if the disk has correct LBA partition
              descriptors. These descriptors should be  present  on  any  disk
              over  8 GiB in size or on smaller disks partitioned with any but
              very ancient software.

       *      BSD disklabel support can create first  and/or  last  partitions
              that overlap with the GPT data structures. This can sometimes be
              compensated by  adjusting  the  partition  table  size,  but  in
              extreme  cases the affected partition(s) may need to be deleted.

       *      Because  of  the  highly  variable  nature  of   BSD   disklabel
              structures,  conversions  from  this  form  may be unreliable --
              partitions may be dropped,  converted  in  a  way  that  creates
              overlaps  with  other  partitions,  or  converted with incorrect
              start or end values. Use this feature with caution!

       *      Booting after converting an MBR or BSD disklabel disk is  likely
              to  be disrupted. Sometimes re-installing a boot loader will fix
              the problem, but  other  times  you  may  need  to  switch  boot
              loaders. Except on EFI-based platforms, Windows through at least
              Windows 7 RC doesn’t support booting from GPT disks. Creating  a
              hybrid   MBR   (using   the   ’h’   option  on  the  recovery  &
              transformation menu) or abandoning GPT in favor of  MBR  may  be
              your only options in this case.

       The  support  for  big-endian CPUs (PowerPC, for example) is new, as of
       version 0.3.5. I advise using caution on  that  platform,  particularly
       with the more obscure features of the program.


       Primary author: Roderick W. Smith (


       * Yves Blusseau (

       * David Hubbard (


       cfdisk (8), fdisk (8), mkfs (8), parted (8), sfdisk (8)


       The  gdisk  command  is  part of the GPT fdisk package and is available
       from Rod Smith.