gdisk

GDISK(8)                       GPT fdisk Manual                       GDISK(8)

NAME
       gdisk - Interactive GUID partition table (GPT) manipulator

SYNOPSIS
       gdisk [ -l ] device

DESCRIPTION
       GPT  fdisk  (aka gdisk) is a text-mode menu-driven program for creation
       and manipulation of partition tables. 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. When used with the -l command-line option, the program
       displays the current partition table and then exits.

       GPT fdisk operates mainly on the GPT headers and partition tables; how-
       ever, it can and will generate a fresh protective MBR,  when  required.
       (Any  boot loader code in the protective MBR will not be disturbed.) If
       you've created an unusual protective MBR, such as a hybrid MBR  created
       by  gptsync or gdisk's own hybrid MBR creation feature, this should not
       be disturbed by most ordinary actions. Some advanced data recovery  op-
       tions  require  you to understand the distinctions between the main and
       backup data, as well as between the GPT headers and the  partition  ta-
       bles.  For  information  on MBR vs. GPT, as well as GPT terminology and
       structure, see the extended  gdisk  documentation  at  http://www.rods-
       books.com/gdisk/ or consult Wikipedia.

       The  gdisk  program employs a user interface similar to that of Linux's
       fdisk, but gdisk modifies GPT partitions. It also has the capability of
       transforming MBR partitions or BSD disklabels into GPT partitions. Like
       the original fdisk program, gdisk 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 'q' option to leave your partitions  un-
       modified.

       Ordinarily,  gdisk  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 in-
       stance)  or  raw  disk images used by emulators such as QEMU or VMWare.
       Note that only raw disk images are supported; gdisk cannot work on com-
       pressed 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  gdisk,  do  not
       need  to  deal  with  CHS  geometries and all the problems they create.
       Users of fdisk will note that gdisk lacks the options  and  limitations
       associated with CHS geometries.

       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 or GNU Parted program.

       Upon start, gdisk attempts to identify the partition type in use on the
       disk.  If  it finds valid GPT data, gdisk will use it. If gdisk 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  Pow-
       erPC-based  Macintoshes.  Upon  exiting  with the 'w' option, gdisk re-
       places the MBR or disklabel with a GPT. This action is potentially dan-
       gerous! Your system may become unbootable, and partition type codes may
       become corrupted if the disk uses unrecognized type codes.  Boot  prob-
       lems  are  particularly likely if you're multi-booting with any GPT-un-
       aware OS. If you mistakenly launch gdisk on an MBR disk, you can safely
       exit the program without making any changes by using the 'q' option.

       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' 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  cre-
              ated 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  par-
              tition  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  con-
              sult your boot loader documentation for details.

       *      If  Windows  is to boot from a GPT disk, a partition of type Mi-
              crosoft Reserved (gdisk 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
       -l     List the partition table for the specified device and  then  ex-
              its.

       Most  interactions  with  gdisk  occur  with  its interactive text-mode
       menus. Three menus exist: the main menu, the recovery &  transformation
       menu,  and the experts' menu. The main menu provides the functions that
       are most likely to be useful for typical partitioning  tasks,  such  as
       creating and deleting partitions, changing partition type codes, and so
       on. Specific functions are:

       b      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.  Note also that the restore option is on
              the recovery & transformation menu; the backup option is on  the
              main menu to encourage its use.

       c      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.

       d      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.

       i      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 gdisk's
              internal partition type code to a plain type name. The  'i'  op-
              tion displays this information for a single partition.

       l      Display  a  summary of partition types. GPT uses a GUID to iden-
              tify partition types for particular OSes and purposes. For  ease
              of  data entry, gdisk 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 gdisk). Some OSes use a single MBR code but  employ
              many  more  codes in GPT. For these, gdisk adds code numbers se-
              quentially, 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. The type code list may
              optionally  be filtered by a search string; for instance, enter-
              ing linux shows only partition type codes with descriptions that
              include the string Linux. This search is performed case-insensi-
              tively.

       n      Create a new partition. This command is modeled after the equiv-
              alent fdisk option, although some differences exist. You enter a
              partition number, starting sector, and an  ending  sector.  Both
              start and end sectors can be specified in absolute terms as sec-
              tor numbers or as positions measured in kibibytes (K), mebibytes
              (M),  gibibytes  (G),  tebibytes  (T), or pebibytes (P); for in-
              stance, 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. 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 end of the same block for the
              end sector.

       o      Clear out all partition data. This includes GPT header data, all
              partition definitions, and the protective MBR. The sector align-
              ment is reset to the default (1 MiB, or 2048 sectors on  a  disk
              with 512-byte sectors).

       p      Display  basic  partition  summary data. This includes partition
              numbers, starting and ending sector  numbers,  partition  sizes,
              gdisk's  partition  types  codes, and partition names. For addi-
              tional information, use the 'i' command.

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

       r      Enter the recovery & transformation  menu.  This  menu  includes
              emergency  recovery options (to fix damaged GPT data structures)
              and options to transform to or from other partitioning  systems,
              including creating hybrid MBRs.

       s      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  re-
              flected  in  your  device  filenames,  so  you  may need to edit
              /etc/fstab if you use this option.

       t      Change a single partition's type code. You enter the  type  code
              using  a  two-byte hexadecimal number, as described earlier. You
              may also enter a GUID  directly,  if  you  have  one  and  gdisk
              doesn't know it.

       v      Verify  disk. This option checks for a variety of problems, such
              as incorrect CRCs and mismatched main and backup data. This  op-
              tion  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.

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

       x      Enter the experts' menu. Using this option  provides  access  to
              features you can use to get into even more trouble than the main
              menu allows.

       ?      Print the menu. Type this command  (or  any  other  unrecognized
              command) to see a summary of available options.

       The second gdisk menu is the recovery & transformation menu, which pro-
       vides access to data recovery  options  and  features  related  to  the
       transformation  of  partitions between partitioning schemes (converting
       BSD disklabels into GPT partitions or creating  hybrid  MBRs,  for  in-
       stance).   A  few  options  on this menu duplicate functionality on the
       main menu, for the sake of convenience. The options on this menu are:

       b      Rebuild GPT header from backup.  You  can  use  the  backup  GPT
              header  to  rebuild  the  main GPT header with this option. It's
              likely to be useful if your main GPT header was damaged  or  de-
              stroyed (say, by sloppy use of dd).

       c      Load  backup  partition  table.  Ordinarily, gdisk uses only the
              main partition table (although the backup's integrity is checked
              when  you  launch  the program). If the main partition table has
              been damaged, you can use this option to load  the  backup  from
              disk  and  use  it instead. Note that this will almost certainly
              produce no or strange partition entries if you've just converted
              an  MBR disk to GPT format, since there will be no backup parti-
              tion table on disk.

       d      Use main GPT header and  rebuild  the  backup.  This  option  is
              likely to be useful if the backup GPT header has been damaged or
              destroyed.

       e      Load main partition table. This option reloads the  main  parti-
              tion  table  from  disk. It's only likely to be useful if you've
              tried to use the backup partition table (via 'c')  but  it's  in
              worse shape then the main partition table.

       f      Load  MBR  and  build fresh GPT from it. Use this option if your
              GPT is corrupt or conflicts with the MBR and you want to use the
              MBR as the basis for a new set of GPT partitions.

       g      Convert GPT into MBR and exit. This option converts as many par-
              titions as possible into MBR form, destroys the GPT data  struc-
              tures,  saves the new MBR, and exits.  Use this option if you've
              tried GPT and find that MBR works better  for  you.   Note  that
              this  function  generates  up  to four primary MBR partitions or
              three primary partitions and as many logical partitions  as  can
              be generated. Each logical partition requires at least one unal-
              located block immediately before its first block. Therefore,  it
              may be possible to convert a maximum of four partitions on disks
              with tightly-packed partitions; however, if free space  was  in-
              serted  between  partitions  when  they were created, and if the
              disk is under 2 TiB in size, it should be  possible  to  convert
              all the partitions to MBR form.  See also the 'h' option.

       h      Create  a  hybrid  MBR.  This is an ugly workaround that enables
              GPT-unaware OSes, or those that can't boot from a GPT  disk,  to
              access up to three of the partitions on the disk by creating MBR
              entries for them. Note that these hybrid MBR entries can  easily
              go  out  of  sync  with  the  GPT entries, particularly when hy-
              brid-unaware GPT utilities are used to edit the disk.  Thus, you
              may  need to re-create the hybrid MBR if you use such tools. Un-
              like the 'g' option, this option does not support converting any
              partitions into MBR logical partitions.

       i      Show detailed partition information. This option is identical to
              the 'i' option on the main menu.

       l      Load partition data from a backup file. This option is  the  re-
              verse  of  the  'b' option on the main menu. Note that restoring
              partition data from anything but the original disk is not recom-
              mended.

       m      Return  to  the  main  menu.  This  option  enables you to enter
              main-menu commands.

       o      Print protective MBR data. You can see a summary of the  protec-
              tive  MBR's  partitions with this option. This may enable you to
              spot glaring problems or help identify the partitions in  a  hy-
              brid MBR.

       p      Print  the  partition table. This option is identical to the 'p'
              option in the main menu.

       q      Quit without saving changes. This option is identical to the 'q'
              option in the main menu.

       t      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 ad-
              justment. gdisk 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 gdisk being unable to
              convert a BSD disklabel is high compared to  the  likelihood  of
              problems with an MBR conversion.

       v      Verify  disk.  This option is identical to the 'v' option in the
              main menu.

       w      Write table to disk and exit. This option is  identical  to  the
              'w' option in the main menu.

       x      Enter the experts' menu. This option is identical to the 'x' op-
              tion in the main menu.

       ?      Print the menu. This option (or any unrecognized entry) displays
              a summary of the menu options.

       The  third gdisk menu is the experts' menu. This menu provides advanced
       options that aren't closely related to recovery or  transformation  be-
       tween partitioning systems. Its options are:

       a      Set  attributes. GPT provides a 64-bit attributes field that can
              be used to set features for each partition. gdisk supports  four
              attributes:  system partition, read-only, hidden, and do not au-
              tomount. You can set other attributes, but their numbers  aren't
              translated  into anything useful. In practice, most OSes seem to
              ignore these attributes.

       c      Change partition GUID. You can enter a custom unique GUID for  a
              partition  using this option. (Note this refers to the GUID that
              uniquely identifies a partition, not to its type code, which you
              can change with the 't' main-menu option.) Ordinarily, gdisk as-
              signs this number randomly; however, you might  want  to  adjust
              the number manually if you've wound up with the same GUID on two
              partitions because of buggy GUID assignments (hopefully  not  in
              gdisk) or sheer incredible coincidence.

       d      Display  the  sector alignment value. See the description of the
              'l' option for more details.

       e      Move backup GPT data structures to the end of the disk. Use this
              command  if  you've added disks to a RAID array, thus creating a
              virtual disk with space that follows the backup GPT data  struc-
              tures.  This command moves the backup GPT data structures to the
              end of the disk, where they belong.

       f      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 with another utility in order to render all
              GUIDs once again unique.

       g      Change  disk GUID. Each disk has a unique GUID code, which gdisk
              assigns randomly upon creation of the GPT data  structures.  You
              can generate a fresh random GUID or enter one manually with this
              option.

       h      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  hy-
              brid  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.

       i      Show detailed partition information. This option is identical to
              the 'i' option on the main menu.

       j      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      Change  the sector alignment value. Disks with more logical sec-
              tors per  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 1 MiB  boundaries  (2048-sectors
              on disks with 512-byte sectors) by default, which optimizes per-
              formance 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.

       m      Return to the main  menu.  This  option  enables  you  to  enter
              main-menu commands.

       n      Create a new protective MBR. Use this option if the current pro-
              tective MBR is damaged in a way that gdisk doesn't automatically
              detect  and correct, or if you want to convert a hybrid MBR into
              a "pure" GPT with a conventional protective MBR.

       o      Print protective MBR data. You can see a summary of the  protec-
              tive  MBR's  partitions with this option. This may enable you to
              spot glaring problems or help identify the partitions in  a  hy-
              brid MBR.

       p      Print  the  partition table. This option is identical to the 'p'
              option in the main menu.

       q      Quit without saving changes. This option is identical to the 'q'
              option in the main menu.

       r      Enter  the recovery & transformations menu. This option is iden-
              tical to the 'r' option on the main menu.

       s      Resize partition table. The default partition table size is  128
              entries.   Officially,  sizes  of  less  than 16KB (128 entries,
              given the normal entry size) are unsupported by the GPT specifi-
              cation;  however,  in  practice they seem to work, and can some-
              times be useful in converting MBR disks. Larger sizes also  work
              fine.  OSes  may impose their own limits on the number of parti-
              tions, though.

       t      Swap two partitions' entries in the partition table. One  parti-
              tion  may be empty. 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.

       u      Replicate  the  current  device's partition table on another de-
              vice. You will be prompted to type the  new  device's  filename.
              After  the  write  operation completes, you can continue editing
              the original device's partition table.  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  f
              option on the new disk.

       v      Verify  disk.  This option is identical to the 'v' option in the
              main menu.

       z      Zap (destroy) the GPT data structures and exit. Use this  option
              if  you want to repartition a GPT disk using fdisk or some other
              GPT-unaware program.  You'll be given the choice  of  preserving
              the  existing  MBR,  in  case it's a hybrid MBR with salvageable
              partitions or if you've already created new MBR  partitions  and
              want to erase the remnants of your GPT partitions. If you've al-
              ready created new MBR partitions, it's conceivable that this op-
              tion  will  damage the first and/or last MBR partitions! Such an
              event is unlikely, but could occur if your  new  MBR  partitions
              overlap the old GPT data structures.

       ?      Print the menu. This option (or any unrecognized entry) displays
              a summary of the menu options.

       In many cases, you can press the Enter key to select a  default  option
       when entering data. When only one option is possible, gdisk usually by-
       passes the prompt entirely.

BUGS
       Known bugs and limitations include:

       *      The program compiles correctly only on Linux, FreeBSD, Mac OS X,
              and  Windows.  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  and Windows have been tested by the author, al-
              though I've heard of 64-bit  versions  being  successfully  com-
              piled.

       *      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'  command  are  14 characters wide. This
              translates to a limitation of about 45 PiB. On larger disks, the
              displayed columns will go out of alignment.

       *      In  the  Windows version, only ASCII characters are supported in
              the  partition  name  field.  If  an  existing  partition   uses
              non-ASCII  UTF-16  characters, they're likely to be corrupted in
              the 'i' and 'p' menu options' displays; however, they should  be
              preserved  when  loading  and  saving  partitions.  Binaries for
              Linux, FreeBSD, and OS X support full UTF-16 partition names.

       *      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 ex-
              perts' 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 ex-
              treme 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 hy-
              brid  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),   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 gdisk command is part of the GPT fdisk  package  and  is  available
       from Rod Smith.

Roderick W. Smith                    1.0.5                            GDISK(8)
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