SGDISK(8)                      GPT fdisk Manual                      SGDISK(8)

       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 manipula-
       tion  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  com-
       mand-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 pro-
       gram's name is based on sfdisk, but the user options of  the  two  pro-
       grams 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  cre-
              ated 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. I  recommended
              making  this  partition  550  MiB. (Smaller ESPs are common, but
              some EFIs have flaky FAT drivers that necessitate a larger  par-
              tition  for  reliable  operation.) 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. (GRUB2 may optionally use such  a  partition.)  This
              partition  can  typically be quite small (roughly 32 to 200 KiB,
              although 1 MiB is more common in practice), but you should  con-
              sult your boot loader documentation for details.

       *      If  Windows  is to boot from a GPT disk, a partition of type Mi-
              crosoft 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 delim-
       itation. 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 min-
       imal. 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.

       -A,        --attributes=list|[partnum:show|or|nand|xor|=|set|clear|tog-
              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 cur-
              rent 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 pro-
              gram,  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 par-
              tition table but does not disturb the data  within  the  sectors
              originally  allocated  to the partition on the disk. If a corre-
              sponding 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  cre-
              ated  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  struc-
              tures.  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  align-
              ment;  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  parti-
              tion  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.

       -j, --adjust-main-table=sector
              Adjust the location of the main partition table. This  value  is
              normally  2, but it may need to be increased in some cases, such
              as when a system-on-chip (SoC) is hard-coded to read  boot  code
              from  sector  2. I recommend against adjusting this value unless
              doing so is absolutely necessary.

       -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 iden-
              tify 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 loca-
              tions  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  parti-
              tion  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 par-
              tition  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  parti-
              tion  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  parti-
              tion  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  ear-
              lier,    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  repar-
              titioned 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

       -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 Pow-
              erPC (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 trans-
              lates to a limitation of about 45 PiB. On larger disks, the dis-
              played columns will go out of alignment.

       *      The program can load only up to 128 partitions (4 primary parti-
              tions and 124 logical partitions) when converting from MBR  for-
              mat.   This   limit  can  be  raised  by  changing  the  #define
              MAX_MBR_PARTS line in the basicmbr.h source code file and recom-
              piling;   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 sup-
              ported by the most common partition table size.)

       *      Converting from MBR format sometimes fails because  of  insuffi-
              cient 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 struc-
              tures, conversions from this form may be  unreliable  --  parti-
              tions  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 load-
              ers. 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  &  transforma-
              tion  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.

Roderick W. Smith                    1.0.3                           SGDISK(8)
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