Provided by: gdisk_1.0.1-1build1_i386 bug


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


       sgdisk [ options ] device


       GPT  fdisk  is  a  text-mode  menu-driven  package  for  creation   and
       manipulation  of  partition  tables.  It  consists of two programs: the
       text-mode interactive gdisk and the command-line sgdisk. Either program
       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. This man  page
       documents the command-line sgdisk program.

       Some  advanced  data  manipulation  and 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

       The sgdisk program employs a user interface that's  based  entirely  on
       the  command  line, making it suitable for use in scripts or by experts
       who want to make one or two quick changes to a disk. (The  program  may
       query  the  user  when  certain  errors  are  encountered, though.) The
       program's name is based on sfdisk, but the  user  options  of  the  two
       programs are entirely different from one another.

       Ordinarily,  sgdisk  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;  sgdisk  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  sgdisk,  do  not
       need to deal with CHS geometries and all the problems they create.

       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, sgdisk, or GNU Parted programs.

       Upon start, sgdisk attempts to identify the partition type  in  use  on
       the  disk.  If  it  finds valid GPT data, sgdisk will use it. If sgdisk
       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. If you specify any option that results
       in changes to an MBR or BSD disklabel,  sgdisk  ignores  those  changes
       unless  the  -g  (--mbrtogpt),  -z (--zap), or -Z (--zap-all) option is
       used. If you use the -g option, sgdisk 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.

       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  (--sort)  option,
       if  you  like.  (Doing  this  may require you to update your /etc/fstab

       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
              (sgdisk  internal  code  0xEF00)  formatted  as   FAT-32.    The
              recommended  size  of this partition is between 100 and 300 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 (sgdisk 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 (sgdisk 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.


       Some  options  take no arguments, others take one argument (typically a
       partition number),  and  others  take  compound  arguments  with  colon
       delimitation.  For  instance,  -n  (--new)  takes a partition number, a
       starting sector number, and an ending sector number, as  in  sgdisk  -n
       2:2000:50000  /dev/sdc,  which  creates  a  new  partition, numbered 2,
       starting at sector 2000 an ending at sector 50,000, on /dev/sdc.

       Unrelated options may be combined; however, some such combinations will
       be  nonsense  (such  as deleting a partition and then changing its GUID
       type code).  sgdisk interprets options in the order  in  which  they're
       entered,  so  effects can vary depending on order. For instance, sgdisk
       -s -d 2 sorts the partition table entries and then deletes partition  2
       from  the  newly-sorted  list;  but sgdisk -d 2 -s deletes the original
       partition 2 and then sorts the modified partition table.

       Error checking and opportunities to  correct  mistakes  in  sgdisk  are
       minimal. Although the program endeavors to keep the GPT data structures
       legal, it does  not  prompt  for  verification  before  performing  its
       actions.  Unless  you require a command-line-driven program, you should
       use the interactive gdisk instead of sgdisk, since gdisk allows you  to
       quit without saving your changes, should you make a mistake.

       Although  sgdisk  is  based  on the same partition-manipulation code as
       gdisk, sgdisk implements fewer features than its  interactive  sibling.
       Options available in sgdisk are:

       -a, --set-alignment=value
              Set the sector alignment multiple. GPT fdisk aligns the start of
              partitions to sectors that are multiples of  this  value,  which
              defaults  to  1MiB  (2048  on  disks  with  512-byte sectors) on
              freshly formatted disks. This alignment value  is  necessary  to
              obtain  optimum performance with Western Digital Advanced Format
              and similar drives with  larger  physical  than  logical  sector
              sizes, with some types of RAID arrays, and with SSD devices.

              View  or  set  partition  attributes.  Use  list  to see defined
              (known) attribute values. Omit the partition  number  (and  even
              the  device filename) when using this option. The others require
              a partition number. The show and get options  show  the  current
              attribute  settings  (all  attributes  or  for a particular bit,
              respectively). The or, nand, xor,  =,  set,  clear,  and  toggle
              options  enable  you to change the attribute bit value. The set,
              clear, toggle, and get options work on a bit number; the  others
              work  on  a  hexadecimal  bit  mask. For example, type sgdisk -A
              4:set:2 /dev/sdc  to  set  the  bit  2  attribute  (legacy  BIOS
              bootable) on partition 4 on /dev/sdc.

       -b, --backup=file
              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. If the GPT data structures are
              damaged,  the  backup  may  not  accurately  reflect the damaged
              state;  instead,  they  will  reflect  GPT  fdisk's   first-pass
              interpretation of the GPT.

       -c, --change-name=partnum:name
              Change  the  GPT  name of a partition. This name is encoded as a
              UTF-16 string, but proper entry and display of  anything  beyond
              basic  ASCII  values  requires suitable locale and font support.
              For the most part, Linux ignores the partition name, but it  may
              be  important  in  some  OSes.  If  you  want to set a name that
              includes a space, enclose it in quotation marks, as in sgdisk -c
              1:"Sample  Name" /dev/sdb. Note that the GPT name of a partition
              is distinct from the filesystem name, which is  encoded  in  the
              filesystem's data structures.

       -C, --recompute-chs
              Recompute  CHS  values  in protective or hybrid MBR. This option
              can sometimes help if a disk utility, OS, or BIOS  doesn't  like
              the  CHS  values  used  by  the  partitions in the protective or
              hybrid MBR. In particular, the GPT specification requires a  CHS
              value  of  0xFFFFFF  for over-8GiB partitions, but this value is
              technically illegal by the usual standards. Some BIOSes hang  if
              they  encounter  this  value.  This option will recompute a more
              normal CHS value -- 0xFEFFFF for over-8GiB partitions,  enabling
              these BIOSes to boot.

       -d, --delete=partnum
              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.

       -D, --display-alignment
              Display current  sector  alignment  value.  Partitions  will  be
              created  on  multiples  of  the  sector  value  reported by this
              option. You can change the alignment value with the -a option.

       e, --move-second-header
              Move backup GPT data structures to the end of the disk. Use this
              option  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.

       -E, --end-of-largest
              Displays the sector number of the end of the  largest  available
              block  of sectors on the disk. A script may store this value and
              pass it back as part of -n's option to create a partition. If no
              unallocated  sectors  are  available,  this function returns the
              value 0.

       -f, --first-in-largest
              Displays the sector number of the start of the largest available
              block  of sectors on the disk. A script may store this value and
              pass it back as part of -n's option to create a partition. If no
              unallocated  sectors  are  available,  this function returns the
              value  0.  Note  that  this  parameter  is  blind  to  partition
              alignment; when you actually create a partition, its start point
              might be changed from this value.

       -F, --first-aligned-in-largest
              Similar to -f (--first-in-largest), except  returns  the  sector
              number  with  the current alignment correction applied. Use this
              function if you need to compute the actual partition start point
              rather  than a theoretical start point or the actual start point
              if you set the alignment value to 1.

       -g, --mbrtogpt
              Convert an MBR or BSD disklabel disk to a GPT disk. As a  safety
              measure,  use of this option is required on MBR or BSD disklabel
              disks if you intend to save your changes, in  order  to  prevent
              accidentally damaging such disks.

       -G, --randomize-guids
              Randomize  the disk's GUID and all partitions' unique GUIDs (but
              not their partition type code GUIDs). This function may be  used
              after  cloning  a  disk  in order to render all GUIDs once again

       -h, --hybrid
              Create a hybrid  MBR.  This  option  takes  from  one  to  three
              partition  numbers,  separated  by  colons,  as  arguments.  The
              created hybrid MBR places an EFI GPT (type 0xEE) partition first
              in  the  table,  followed by the partition(s) you specify. Their
              type codes are based on the GPT  fdisk  type  codes  divided  by
              0x0100,  which is usually correct for Windows partitions. If the
              active/bootable flag should be set, you must do  so  in  another
              program,  such  as  fdisk.  The  gdisk program offers additional
              hybrid MBR creation options.

       -i, --info=partnum
              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  sgdisk's
              internal partition type code to a plain type name. The -i option
              displays this information for a single partition.

       -l, --load-backup=file
              Load partition data from a  backup  file.  This  option  is  the
              reverse  of  the  -b  option. Note that restoring partition data
              from anything but the original disk  is  not  recommended.  This
              option  will work even if the disk's original partition table is
              bad; however, most other options on the same command  line  will
              be ignored.

       -L, --list-types
              Display  a  summary  of  partition  types.  GPT  uses  a GUID to
              identify partition types for particular OSes and  purposes.  For
              ease  of  data  entry,  sgdisk  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,  the  codes
              for  all  varieties  of  FAT  and NTFS partition correspond to a
              single GPT code (entered as 0x0700 in sgdisk). Some OSes  use  a
              single  MBR  code  but employ many more codes in GPT. For these,
              sgdisk 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  and sgdisk. This option does not require you to specify a
              valid disk device filename.

       -m, --gpttombr
              Convert disk from GPT to MBR form. This option takes from one to
              four partition numbers, separated by colons, as arguments. Their
              type codes are based on the GPT  fdisk  type  codes  divided  by
              0x0100.  If  the active/bootable flag should be set, you must do
              so in another program, such as fdisk.  The gdisk program  offers
              additional MBR conversion options. It is not possible to convert
              more than four partitions from GPT to MBR  form  or  to  convert
              partitions  that  start  above  the 2TiB mark or that are larger
              than 2TiB.

       -n, --new=partnum:start:end
              Create a new partition. 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  kibibytes  (K),  mebibytes  (M),  gibibytes  (G),
              tebibytes (T), or pebibytes (P); 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  default
              range  by preceding the number by a '+' or '-' symbol, as in +2G
              to specify a point 2GiB after the default start sector, or -200M
              to  specify  a  point 200MiB before the last available sector. A
              start or end value of 0 specifies the default  value,  which  is
              the  start  of  the largest available block for the start sector
              and the end of the same block for  the  end  sector.  A  partnum
              value  of  0  causes  the  program  to  use  the first available
              partition number. Subsequent uses of the  -A,  -c,  -t,  and  -u
              options may also use 0 to refer to the same partition.

       -N, --largest-new=num
              Create a new partition that fills the largest available block of
              space on the disk. You can use the -a  (--set-alignment)  option
              to adjust the alignment, if desired. A num value of 0 causes the
              program to use the first available partition number.

       -o, --clear
              Clear out all partition data. This includes GPT header data, all
              partition  definitions,  and  the protective MBR. Note that this
              operation will, like most other operations, fail  on  a  damaged
              disk.  If  you want to prepare a disk you know to be damaged for
              GPT use, you should first wipe it with -Z and then partition  it
              normally.  This  option  will  work  even if the disk's original
              partition table is bad; however, most other options on the  same
              command line will be ignored.

       -O, --print-mbr
              Display   basic   MBR  partition  summary  data.  This  includes
              partition numbers, starting and ending sector numbers, partition
              sizes,  MBR  partition  types  codes,  and partition names. This
              option is useful mainly for diagnosing partition table problems,
              particularly on disks with hybrid MBRs.

       -p, --print
              Display   basic   GPT  partition  summary  data.  This  includes
              partition numbers, starting and ending sector numbers, partition
              sizes,  sgdisk's partition types codes, and partition names. For
              additional information, use the -i (--info) option.

       -P, --pretend
              Pretend to make specified changes. In-memory GPT data structures
              are  altered  according to other parameters, but changes are not
              written to disk.

       -r, --transpose
              Swap two partitions' entries in the partition table. One or both
              partitions  may be empty, although swapping two empty partitions
              is pointless. For  instance,  if  partitions  1-4  are  defined,
              transposing  1 and 5 results in a table with partitions numbered
              from 2-5. Transposing partitions in this way has  no  effect  on
              their  disk  space allocation; it only alters their order in the
              partition table.

       -R, --replicate=second_device_filename
              Replicate the main device's partition  table  on  the  specified
              second  device.   Note that the replicated partition table is an
              exact copy, including all GUIDs; if the device should  have  its
              own unique GUIDs, you should use the -G option on the new disk.

       -s, --sort
              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, --typecode=partnum:{hexcode|GUID}
              Change a single partition's type code. You enter the  type  code
              using   either  a  two-byte  hexadecimal  number,  as  described
              earlier,   or   a   fully-specified   GUID   value,   such    as

       -T, --transform-bsd=partnum
              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. sgdisk 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 sgdisk being unable
              to convert a BSD disklabel is high compared to the likelihood of
              problems with an MBR conversion.

       -u, --partition-guid=partnum:guid
              Set  the  partition unique GUID for an individual partition. The
              GUID may be a complete GUID or 'R' to set a random GUID.

       -U, --disk-guid=guid
              Set the GUID for the disk. The GUID may be a  complete  GUID  or
              'R' to set a random GUID.

              Print a brief summary of available options.

       -v, --verify
              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. This option will  work  even  if  the
              disk's  original  partition  table  is  bad; however, most other
              options on the same command line will be ignored.

       -V, --version
              Display program version information. This  option  may  be  used
              without specifying a device filename.

       -z, --zap
              Zap  (destroy)  the  GPT data structures and then exit. Use this
              option if you want to repartition a GPT disk using fdisk or some
              other  GPT-unaware  program.  This  option destroys only the GPT
              data structures; it leaves the MBR intact. This makes it  useful
              for  wiping  out  GPT  data  structures  after  a  disk has been
              repartitioned for MBR  using  a  GPT-unaware  utility;  however,
              there's  a  risk  that  it  will damage boot loaders or even the
              start of the first or end of the last MBR partition. If you  use
              it  on  a  valid  GPT  disk,  the  MBR  will  be  left  with  an
              inappropriate EFI GPT (0xEE) partition definition, which you can
              delete using another utility.

       -Z, --zap-all
              Zap  (destroy)  the  GPT  and MBR data structures and then exit.
              This option works much like -z, but as it wipes the MBR as  well
              as the GPT, it's more suitable if you want to repartition a disk
              after using this option, and  completely  unsuitable  if  you've
              already repartitioned the disk.

       -?, --help
              Print a summary of options.


       sgdisk returns various values depending on its success or failure:

       0      Normal program execution

       1      Too few arguments

       2      An error occurred while reading the partition table

       3      Non-GPT disk detected and no -g option, but operation requires a
              write action

       4      An error prevented saving changes

       5      An error occurred while reading  standard  input  (should  never
              occur with sgdisk, but may with gdisk)

       8      Disk replication operation (-R) failed


       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 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.) This limitation can be
              overcome by typing sysctl  kern.geom.debugflags=16  at  a  shell

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

       *      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  basicmbr.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.


       Primary author: Roderick W. Smith (


       * Yves Blusseau (

       * David Hubbard (

       * Justin Maggard (

       * Dwight Schauer (

       * Florian Zumbiehl (


       cfdisk  (8),  cgdisk  (8),  fdisk (8), gdisk (8), mkfs (8), parted (8),
       sfdisk (8) fixparts (8)


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