Provided by: gdisk_1.0.4-3_amd64 bug

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 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 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  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 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  created in whatever order and in
              whatever sizes are desired.

       *      Boot disks for EFI-based systems require an EFI System  Partition  (gdisk  internal
              code  0xEF00)  formatted  as  FAT-32.  I recommended making this partition 550 MiB.
              (Smaller ESPs are common, but some EFIs have flaky FAT drivers that  necessitate  a
              larger partition 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 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.

OPTIONS

       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.

       -A,
       --attributes=list|[partnum:show|or|nand|xor|=|set|clear|toggle|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  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 unique.

       -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.

       -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 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 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 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.

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, 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

BUGS

       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 prompt.

       *      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.

AUTHORS

       Primary author: Roderick W. Smith (rodsmith@rodsbooks.com)

       Contributors:

       * Yves Blusseau (1otnwmz02@sneakemail.com)

       * David Hubbard (david.c.hubbard@gmail.com)

       * Justin Maggard (justin.maggard@netgear.com)

       * Dwight Schauer (dschauer@gmail.com)

       * Florian Zumbiehl (florz@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.