Provided by: gdisk_1.0.8-4build1_amd64 bug

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;  however,  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 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 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 unmodified.

       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
       instance)  or raw disk images used by emulators such as QEMU or VMWare. Note that only raw
       disk images are supported; gdisk 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
       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 PowerPC-based Macintoshes. Upon exiting with the
       'w' option, gdisk 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 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  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
              (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 exits.

       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  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. 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 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.

       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'
              option displays this information for a single partition.

       l      Display  a  summary of partition types. GPT uses a GUID to identify 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 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. 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.

       n      Create a new partition. This command is modeled after the equivalent 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
              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. 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 alignment 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 additional information, use the 'i' command.

       q      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.

       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  reflected  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 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.

       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 provides 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 instance).  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 destroyed (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 partition 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 partition 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 partitions as  possible
              into MBR form, destroys the GPT data structures, 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  unallocated 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 inserted 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 hybrid-unaware GPT
              utilities are used to edit the disk.  Thus, you may need to  re-create  the  hybrid
              MBR  if  you  use  such  tools. Unlike 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 reverse of the 'b'
              option on the main menu. Note that restoring partition data from anything  but  the
              original disk is not recommended.

       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 protective MBR's partitions
              with this option. This may enable you to spot glaring problems or help identify the
              partitions in a hybrid 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  adjustment.  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'  option  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 between 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 automount. You can set other  attributes,  but  their
              numbers  aren't  translated  into  anything  useful. In practice, most OSes seem to
              ignore these attributes.

       b      Swap the byte order for the name of  the  specified  partition.  Some  partitioning
              tools,  including  GPT fdisk 1.0.7 and earlier, can write the partition name in the
              wrong byte order on big-endian computers, such  as  the  IBM  s390  mainframes  and
              PowerPC-based Macs. This feature corrects this problem.

       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 assigns 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 structures. 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 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.

       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  sectors  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 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.

       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 protective 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 protective MBR's partitions
              with this option. This may enable you to spot glaring problems or help identify the
              partitions in a hybrid 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 identical 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 specification; however, in practice they seem to  work,  and
              can  sometimes be useful in converting MBR disks. Larger sizes also work fine. OSes
              may impose their own limits on the number of partitions, though.

       t      Swap two partitions' entries in the partition table. One partition  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 device. 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 already created new MBR
              partitions, it's conceivable that this option 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 bypasses 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,  although  I've  heard  of  64-bit
              versions being successfully compiled.

       *      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  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  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 (das@teegra.net)

       * 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.