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NAME

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

SYNOPSIS

       cgdisk [ -a ] device

DESCRIPTION

       GPT  fdisk  is  a  text-mode family of programs for creation and manipulation 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 Table (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 structure, see the extended
       GPT fdisk documentation at http://www.rodsbooks.com/gdisk/ 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 structures until you explicitly write them to disk, so if you make a mistake, 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 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  (GPT  fdisk
              internal  code 0xEF00) formatted as FAT-32.  The recommended size of this partition
              is between 100 and 300 MiB.  Boot-related files are stored  here.  (Note  that  GNU
              Parted identifies 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  documentation
              for details.

       *      If  Windows is to boot from a GPT disk, a partition of type Microsoft Reserved (GPT
              fdisk 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 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.

OPTIONS

       Only  one command-line option is accepted, aside from the device filename: -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 appear.

       In  addition,  the  top  of  the  display shows the program's name and version 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 option.

       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 modification, or other  advanced  operations,  you  should  consult  the  gdisk
       documentation.)

       Align  Change  the  sector  alignment value. Disks with more logical sectors 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 properly
              for their internal data structures. On new  disks,  GPT  fdisk  attempts  to  align
              partitions  on  1  MiB  boundaries (2048-sectors on disks with 512-byte sectors) 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.  The alignment value also affects the default end  sector  value  when
              creating  a  new  partition;  it will be aligned to one less than a multiple of the
              alignment value, when possible. This should  keep  partitions  a  multiple  of  the
              alignment  value in size. Some disk encryption tools require partitions to be sized
              to some value, typically 4096 bytes, so the default alignment of 1 MiB  works  well
              for them.

       Backup 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.

       Delete 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.

       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 partitions' sector-exact start and end points.  The  Info  option  displays
              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 option....

       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 specifies the default value,
              which is the start of the largest available 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.  The type code list may optionally  be  filtered
              by  a  search  string; for instance, entering linux shows only partition type codes
              with  descriptions  that  include  the  string  Linux.  This  search  is  performed
              case-insensitively.

       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.

BUGS

       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 prompt.

       *      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 in gdisk) 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 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 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  doesn't  support  booting  from GPT disks. Creating a hybrid MBR
              (using the 'h' option on the recovery & transformation 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.

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 (das@teegra.net)

       * Florian Zumbiehl (florz@florz.de)

SEE ALSO

       cfdisk(8), fdisk(8), gdisk(8), mkfs(8), parted(8), sfdisk(8), sgdisk(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 cgdisk command is part of the GPT fdisk package and is available from Rod Smith.