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CGDISK(8)		       GPT fdisk Manual			     CGDISK(8)

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

       cgdisk [ -a ] 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.

       Only  one  command-line option is accepted, aside from the device file‐
       name: -a. This option alters the highlighting of partitions and	blocks
       of  free space: Instead of using ncurses, when -a is used cgdisk uses a
       ">" symbol to the left of the selected partition or free	 space.	  This
       option is intended for use on limited display devices such as teletypes
       and screen readers.

       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  March  2014  (version 0.8.10), 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		    0.8.10			     CGDISK(8)

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