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CGDISK(8)		       GPT fdisk Manual			     CGDISK(8)

       cgdisk - Curses-based GUID partition table (GPT) manipulator

       cgdisk device

       GPT  fdisk is a text-mode family of programs for creation and manipula‐
       tion of partition tables. The cgdisk member of this  family  employs  a
       curses-based  user  interface for interaction using a text-mode menuing
       system. It 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  Ta‐
       ble (GPT) format, or will load a GUID partition table. Other members of
       this program family are gdisk (the most	feature-rich  program  of  the
       group,  with  a non-curses-based interactive user interface) and sgdisk
       (which is driven via command-line options for  use  by  experts	or  in
       scripts).   FixParts  is	 a related program for fixing a limited set of
       problems with MBR disks.

       For information on MBR vs. GPT, as well as GPT terminology  and	struc‐
       ture,  see  the	extended  GPT  fdisk documentation at http://www.rods‐ or consult Wikipedia.

       The cgdisk program employs a user interface similar to that of  Linux's
       cfdisk,	but cgdisk modifies GPT partitions. It also has the capability
       of transforming MBR partitions or BSD disklabels into  GPT  partitions.
       Like  the  original  cfdisk program, cgdisk does not modify disk struc‐
       tures until you explicitly write them to disk, so if you	 make  a  mis‐
       take,  you can exit from the program with the Quit option to leave your
       partitions unmodified.

       Ordinarily, cgdisk 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; cgdisk cannot work on
       compressed or other advanced disk image formats.

       Upon start, cgdisk attempts to identify the partition type  in  use  on
       the  disk.  If  it  finds valid GPT data, cgdisk will use it. If cgdisk
       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.)  Upon  exiting with the 'w'
       option, cgdisk 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. If you mistakenly  launch  cgdisk  on  an  MBR
       disk,  you  can	safely	exit the program without making any changes by
       using the Quit option.

       When creating a fresh partition table, certain considerations may be in

       *      For data (non-boot) disks, and for boot disks used on BIOS-based
	      computers with GRUB as the boot loader, partitions may  be  cre‐
	      ated in whatever order and in whatever sizes are desired.

       *      Boot disks for EFI-based systems require an EFI System Partition
	      (GPT fdisk internal code 0xEF00) formatted as FAT-32.  The  rec‐
	      ommended	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.)

       *      The  GRUB	 2  boot  loader for BIOS-based systems makes use of a
	      BIOS Boot Partition (GPT fdisk internal code 0xEF02),  in	 which
	      the  secondary  boot  loader is stored, without the benefit of a
	      filesystem. This partition can typically be quite small (roughly
	      32  KiB to 1 MiB), but you should consult your boot loader docu‐
	      mentation for details.

       *      If Windows is to boot from a GPT disk, a partition of  type  Mi‐
	      crosoft  Reserved	 (GPT  fdisk  internal	code 0x0C01) is recom‐
	      mended. This partition should be about 128 MiB in size. It ordi‐
	      narily follows the EFI System Partition and immediately precedes
	      the Windows data partitions. (Note  that	old  versions  of  GNU
	      Parted  create  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.
	      You  can	use  GPT fdisk's relative partition positioning option
	      (specifying the starting sector as  '+128M',  for	 instance)  to
	      simplify creating such gaps.

       Interactions  with  cgdisk  occur with its interactive text-mode menus.
       The display is broken into two interactive parts:

       *      The partition display area, in which partitions and gaps between
	      them (marked as "free space") are summarized.

       *      The option selection area, in which buttons for the main options

       In addition, the top of the display shows the program's name  and  ver‐
       sion  number,  the  device  filename  associated with the disk, and the
       disk's size in both sectors and IEEE-1541 units (GiB, TiB, and so on).

       You can use the following keys to move among the various options and to
       select among them:

       up arrow
	      This key moves the partition selection up by one partition.

       down arrow
	      This key moves the partition selection down by one partition.

       Page Up
	      This key moves the partition selection up by one screen.

       Page Down
	      This key moves the partition selection down by one screen.

       right arrow
	      This key moves the option selection to the right by one item.

       left arrow
	      This key moves the option selection to the left by one item.

       Enter  This  key	 activates the currently selected option. You can also
	      activate an option by  typing  the  capitalized  letter  in  the
	      option's	name  on the keyboard, such as a to activate the Align

       If more partitions exist than can be displayed in one screen,  you  can
       scroll between screens using the partition selection keys, much as in a
       text editor.

       Available options are as described below. (Note that cgdisk provides  a
       much more limited set of options than its sibling gdisk. If you need to
       perform partition table recovery,  hybrid  MBR  modifcation,  or	 other
       advanced operations, you should consult the gdisk documentation.)

       Align  Change  the sector alignment value. Disks with more logical sec‐
	      tors than physical  sectors  (such  as  modern  Advanced	Format
	      drives),	some  RAID  configurations,  and many SSD devices, can
	      suffer performance problems if partitions are not aligned	 prop‐
	      erly for their internal data structures. On new disks, GPT fdisk
	      attempts to align partitions on 2048-sector (1MiB) boundaries by
	      default,	which  optimizes  performance  for  all	 of these disk
	      types. On pre-partitioned disks, GPT fdisk attempts to  identify
	      the  alignment  value  used  on that disk, but will set 8-sector
	      alignment on disks larger than 300 GB even if  lesser  alignment
	      values  are detected. In either case, it can be changed by using
	      this option.

       Backup 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.

       Delete 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.

       Help   Print brief descriptions of all the options.

       Info   Show detailed partition  information.  The  summary  information
	      shown  in	 the  partition	 display  area	necessarily omits many
	      details, such as the partitions' unique  GUIDs  and  the	parti‐
	      tions'  sector-exact  start and end points. The Info option dis‐
	      plays this information for a single partition.

       Load   Load partition data from a  backup  file.	 This  option  is  the
	      reverse of the Backup option. Note that restoring partition data
	      from anything but the original disk is not recommended.

       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. GPT fdisk sets a default  name	 based
	      on  the partition type code. Note that the GPT partition name is
	      different from the filesystem name,  which  is  encoded  in  the
	      filesystem's  data  structures.  Note also that to activate this
	      item by typing its alphabetic equivalent, you must  use  M,  not
	      the  more	 obvious  N,  because  the  latter is used by the next

       New    Create a new partition. You enter a starting sector, a  size,  a
	      type  code,  and	a  name.  The start sector can be specified in
	      absolute terms as a sector number or as a position  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 '+' symbol, as in +2G to specify a point 2GiB after
	      the default start sector. The size value can use the K, M, G, T,
	      and P suffixes, too. Pressing the Enter key with no input speci‐
	      fies the default value, which is the start of the largest avail‐
	      able  block for the start sector and the full available size for
	      the size.

       Quit   Quit from the program without saving  your  changes.   Use  this
	      option  if  you just wanted to view information or if you make a
	      mistake and want to back out of all your changes.

       Type   Change a single partition's type code. You enter the  type  code
	      using  a	two-byte hexadecimal number. You may also enter a GUID
	      directly, if you have one and cgdisk doesn't  know  it.  If  you
	      don't  know  the type code for your partition, you can type L to
	      see a list of known type codes.

       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 gdisk. If no problems are found, this command
	      displays a summary of unallocated disk space.

       Write  Write data. Use this command to save your changes.

       As of January 2013 (version 0.8.6), cgdisk should  be  considered  beta
       software.  Although  the underlying partition manipulation code is much
       older, the cgdisk ncurses user interface is brand new  with  GPT	 fdisk
       version 0.8.0. Known bugs and limitations include:

       *      The  program  compiles correctly only on Linux, FreeBSD, and Mac
	      OS X. In theory, it should compile under Windows if the  Ncurses
	      library  for  Windows  is	 installed, but I have not tested this
	      capability. 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. Under FreeBSD,  32-bit  (x86)  and
	      64-bit  (x86-64) versions have been tested. Only 32-bit versions
	      for Mac OS X has been tested by the author.

       *      The FreeBSD version of the program can't write  changes  to  the
	      partition	 table to a disk when existing partitions on that disk
	      are mounted. (The same problem exists with  many	other  FreeBSD
	      utilities,  such	as gpt, fdisk, and dd.) This limitation can be
	      overcome by typing sysctl	 kern.geom.debugflags=16  at  a	 shell

       *      The 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  in  gdisk)  can sometimes overcome this problem;
	      however, in extreme cases it may be necessary to resize a parti‐
	      tion using GNU Parted or a similar tool prior to conversion with
	      GPT fdisk.

       *      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 doesn't support booting from  GPT  disks.  Creating  a
	      hybrid  MBR  (using the 'h' option on the recovery & transforma‐
	      tion menu in gdisk) or abandoning GPT in favor  of  MBR  may  be
	      your only options in this case.

       *      The  cgdisk  Verify  function  and  the  partition  type listing
	      obtainable by typing L in the Type function (or when  specifying
	      a	 partition type while creating a new partition) both currently
	      exit ncurses mode. This limitation is a minor  cosmetic  blemish
	      that does not affect functionality.

       Primary author: Roderick W. Smith (


       * Yves Blusseau (

       * David Hubbard (

       * Justin Maggard (

       * Dwight Schauer (

       * Florian Zumbiehl (

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

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

Roderick W. Smith		     0.8.6			     CGDISK(8)

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