gdisk

```
[root@xxxx linuxstudy]# fdisk  -l /dev/sdb
WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.

Disk /dev/sdb: 8589 MB, 8589934592 bytes, 16777216 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O サイズ (最小 / 推奨): 512 バイト / 512 バイト
Disk label type: gpt
Disk identifier: 290C4890-AEDA-4A7F-AFD7-3AF77DF306CE


#         Start          End    Size  Type            Name
 1         2048        10000    3.9M  Linux filesyste 
 2        10240        20000    4.8M  Linux filesyste 
[root@xxxx linuxstudy]# gdisk
GPT fdisk (gdisk) version 0.8.10

Type device filename, or press <Enter> to exit: q
Problem opening q for reading! Error is 2.
The specified file does not exist!
[root@xxxx linuxstudy]# gdisk /dev/sdb
GPT fdisk (gdisk) version 0.8.10

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): ?
b	back up GPT data to a file
c	change a partition's name
d	delete a partition
i	show detailed information on a partition
l	list known partition types
n	add a new partition
o	create a new empty GUID partition table (GPT)
p	print the partition table
q	quit without saving changes
r	recovery and transformation options (experts only)
s	sort partitions
t	change a partition's type code
v	verify disk
w	write table to disk and exit
x	extra functionality (experts only)
?	print this menu

Command (? for help): p
Disk /dev/sdb: 16777216 sectors, 8.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 290C4890-AEDA-4A7F-AFD7-3AF77DF306CE
Partition table holds up to 128 entries
First usable sector is 2048, last usable sector is 16777182
Partitions will be aligned on 2048-sector boundaries
Total free space is 16757421 sectors (8.0 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048           10000   3.9 MiB     8300  
   2           10240           20000   4.8 MiB     8300  

Command (? for help): n
Partition number (3-128, default 3): 
First sector (10001-16777182, default = 20480) or {+-}size{KMGTP}: 
Last sector (20480-16777182, default = 16777182) or {+-}size{KMGTP}: 40000
Current type is 'Linux filesystem'
Hex code or GUID (L to show codes, Enter = 8300): L
0700 Microsoft basic data  0c01 Microsoft reserved    2700 Windows RE          
3000 ONIE boot             3001 ONIE config           4100 PowerPC PReP boot   
4200 Windows LDM data      4201 Windows LDM metadata  7501 IBM GPFS            
7f00 ChromeOS kernel       7f01 ChromeOS root         7f02 ChromeOS reserved   
8200 Linux swap            8300 Linux filesystem      8301 Linux reserved      
8302 Linux /home           8400 Intel Rapid Start     8e00 Linux LVM           
a500 FreeBSD disklabel     a501 FreeBSD boot          a502 FreeBSD swap        
a503 FreeBSD UFS           a504 FreeBSD ZFS           a505 FreeBSD Vinum/RAID  
a580 Midnight BSD data     a581 Midnight BSD boot     a582 Midnight BSD swap   
a583 Midnight BSD UFS      a584 Midnight BSD ZFS      a585 Midnight BSD Vinum  
a800 Apple UFS             a901 NetBSD swap           a902 NetBSD FFS          
a903 NetBSD LFS            a904 NetBSD concatenated   a905 NetBSD encrypted    
a906 NetBSD RAID           ab00 Apple boot            af00 Apple HFS/HFS+      
af01 Apple RAID            af02 Apple RAID offline    af03 Apple label         
af04 AppleTV recovery      af05 Apple Core Storage    be00 Solaris boot        
bf00 Solaris root          bf01 Solaris /usr & Mac Z  bf02 Solaris swap        
bf03 Solaris backup        bf04 Solaris /var          bf05 Solaris /home       
bf06 Solaris alternate se  bf07 Solaris Reserved 1    bf08 Solaris Reserved 2  
bf09 Solaris Reserved 3    bf0a Solaris Reserved 4    bf0b Solaris Reserved 5  
c001 HP-UX data            c002 HP-UX service         ea00 Freedesktop $BOOT   
eb00 Haiku BFS             ed00 Sony system partitio  ed01 Lenovo system partit
Press the <Enter> key to see more codes: 7f01
ef00 EFI System            ef01 MBR partition scheme  ef02 BIOS boot partition 
fb00 VMWare VMFS           fb01 VMWare reserved       fc00 VMWare kcore crash p
fd00 Linux RAID            
Hex code or GUID (L to show codes, Enter = 8300): 7f01
Changed type of partition to 'ChromeOS root'

Command (? for help): p
Disk /dev/sdb: 16777216 sectors, 8.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 290C4890-AEDA-4A7F-AFD7-3AF77DF306CE
Partition table holds up to 128 entries
First usable sector is 2048, last usable sector is 16777182
Partitions will be aligned on 2048-sector boundaries
Total free space is 16737900 sectors (8.0 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048           10000   3.9 MiB     8300  
   2           10240           20000   4.8 MiB     8300  
   3           20480           40000   9.5 MiB     7F01  ChromeOS root

```
```
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
       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.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
       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 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
       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 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.  The recom‐
              mended 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.)


       *      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),
              but  you  should  consult  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
              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 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'
              option 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 sgdisk). 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.


       n      Create  a  new  partition.  This  command  is modelled 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 align‐
              ment is reset to the default (2048 sectors, or 1MB).


       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
              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 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
       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 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
              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 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
              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.


       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  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
              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.


       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 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.


       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
              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 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
              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
       As of March 2014 (version 0.8.10),  gdisk  should  be  considered  beta
       software. 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 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
              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 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)  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@ti.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                   0.8.10                            GDISK(8)```