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SGDISK(8)                      GPT fdisk Manual                      SGDISK(8)

NAME
       sgdisk  - Command-line GUID partition table (GPT) manipulator for Linux
       and Unix
SYNOPSIS
       sgdisk [ options ] device

DESCRIPTION
       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  http://www.rodsbooks.com/gdisk/  or  consult
       Wikipedia.
       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
       file.)
       When creating a fresh partition table, certain considerations may be in
       order:

       *      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
              (sgdisk internal code 0xEF00) formatted as FAT-32.   The  recom-
              mended  size  of  this  partition  is  between  100 and 300 MiB.
              Boot-related files are stored here. (Note that GNU Parted  iden-
              tifies 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 documen-
              tation 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.

OPTIONS
       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  2048  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-
       gle|get[:bitnum|hexbitmask]]
              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
              unique.

       -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.

       -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. Note that if used on a completely blank disk,
              this  is  likely  to result in a sector-moved warning, since the
              first available sector (normally 34) doesn't fall on a 2048-sec-
              tor  boundary  (the  default  for alignment). 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.

       -p, --print
              Display  basic  partition  summary data. This includes partition
              numbers, starting and ending sector  numbers,  partition  sizes,
              sgdisk's  partition  types codes, and partition names. For addi-
              tional 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
              EBD0A0A2-B9E5-4433-87C0-68B6B72699C7.

       -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.

       --usage
              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
              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.

RETURN VALUES
       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

       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

BUGS
       As of March 2014 (version 0.8.10), sgdisk  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 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
              prompt.

       *      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.

AUTHORS
       Primary author: Roderick W. Smith (rodsmith AT rodsbooks.com)
       Contributors:
       * Yves Blusseau (1otnwmz02 AT sneakemail.com)
       * David Hubbard (david.c.hubbard AT gmail.com)
       * Justin Maggard (justin.maggard AT netgear.com)
       * Dwight Schauer (dschauer AT ti.com)
       * Florian Zumbiehl (florz AT florz.de)

SEE ALSO
       cfdisk  (8),  cgdisk  (8),  fdisk (8), gdisk (8), mkfs (8), parted (8),
       sfdisk (8) fixparts (8)
       http://en.wikipedia.org/wiki/GUID_Partition_Table
       http://developer.apple.com/technotes/tn2006/tn2166.html
       http://www.rodsbooks.com/gdisk/

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

Roderick W. Smith                   0.8.10                           SGDISK(8)