bionic (8) sgdisk.8.gz

Provided by: gdisk_1.0.3-1_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.