-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. Default start and end points may be adjusted to optimize partition
alignment.
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 withoutsavingyourchanges. 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: systempartition, read-only, hidden, and donotautomount. 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.
k Adjust the location of the backup partition table. This partition table is normally located just
before the backup metadata at the end of the disk, but it may need to be moved in some very rare
cases. 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. The alignment value also
affects the default end sector value when creating a new partition; it will be aligned to one less
than a multiple of the alignment value, if possible. This should keep partitions a multiple of the
alignment value in size. Some disk encryption tools require partitions to be sized to some value,
typically 4096 bytes, so the default alignment of 1 MiB works well for them.
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. Ifyou'vealreadycreatednewMBRpartitions,it'sconceivablethatthisoptionwilldamagethefirstand/orlastMBRpartitions! 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.
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