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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | DEVICES | SIZES | SCRIPT FILES | DISK LABELS | DOS MODE AND DOS 6.X WARNING | COLORS | ENVIRONMENT | AUTHORS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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FDISK(8) System Administration FDISK(8)
fdisk - manipulate disk partition table
fdisk [options] device
fdisk -l [device...]
fdisk is a dialog-driven program for creation and manipulation of
partition tables. It understands GPT, MBR, Sun, SGI and BSD
partition tables.
Block devices can be divided into one or more logical disks called
partitions. This division is recorded in the partition table,
usually found in sector 0 of the disk. (In the BSD world one talks
about `disk slices' and a `disklabel'.)
All partitioning is driven by device I/O limits (the topology) by
default. fdisk is able to optimize the disk layout for a 4K-sector
size and use an alignment offset on modern devices for MBR and
GPT. It is always a good idea to follow fdisk's defaults as the
default values (e.g., first and last partition sectors) and
partition sizes specified by the +/-<size>{M,G,...} notation are
always aligned according to the device properties.
CHS (Cylinder-Head-Sector) addressing is deprecated and not used
by default. Please, do not follow old articles and recommendations
with fdisk -S <n> -H <n> advice for SSD or 4K-sector devices.
Note that partx(8) provides a rich interface for scripts to print
disk layouts, fdisk is mostly designed for humans. Backward
compatibility in the output of fdisk is not guaranteed. The input
(the commands) should always be backward compatible.
-b, --sector-size sectorsize
Specify the sector size of the disk. Valid values are 512,
1024, 2048, and 4096. The kernel is aware of the sector size
for regular block devices. Use this option only on very old
kernels, when working with disk images, or to override the
kernel’s default sector size. Since util-linux-2.17, fdisk
distinguishes between logical and physical sector size. This
option changes both sector sizes to the specified sectorsize.
-B, --protect-boot
Don’t erase the beginning of the first disk sector when
creating a new disk label. This feature is supported for GPT
and MBR.
-c, --compatibility[=mode]
Specify the compatibility mode, 'dos' or 'nondos'. The default
is non-DOS mode. For backward compatibility, it is possible to
use the option without the mode argument — then the default is
used. Note that the optional mode argument cannot be separated
from the -c option by a space, the correct form is for example
-c=dos.
-L, --color[=when]
Colorize the output. The optional argument when can be auto,
never or always. If the when argument is omitted, it defaults
to auto. The colors can be disabled; for the current built-in
default see the --help output. See also the COLORS section.
-l, --list
List the partition tables for the specified devices and then
exit.
If no devices are given, the devices mentioned in
/proc/partitions (if this file exists) are used. Devices are
always listed in the order in which they are specified on the
command-line, or by the kernel listed in /proc/partitions.
-x, --list-details
Like --list, but provides more details.
--lock[=mode]
Use an exclusive BSD lock for the device or file that is
operated upon. The optional argument mode can be yes (1), no
(0), or nonblock. If the mode argument is omitted, it defaults
to yes. This option overrides the environment variable
$LOCK_BLOCK_DEVICE. The default is to not use any lock at all,
but using a lock is recommended to avoid collisions with
systemd-udevd(8) or other tools.
-n, --noauto-pt
Don’t automatically create a default partition table on empty
device. The partition table has to be explicitly created by
user (by command like 'o', 'g', etc.).
-o, --output list
Specify which output columns to print. Use --help to get a
list of all supported columns.
The default list of columns may be extended if list is
specified in the format +list (e.g., -o +UUID).
-s, --getsz
Print the size in 512-byte sectors of each given block device.
This option is DEPRECATED in favour of blockdev(8).
-t, --type type
Enable support only for disklabels of the specified type, and
disable support for all other types.
-u, --units[=unit]
When listing partition tables, show sizes in 'sectors' or in
'cylinders'. The default is to show sizes in sectors. For
backward compatibility, it is possible to use the option
without the unit argument — then the default is used. Note
that the optional unit argument cannot be separated from the
-u option by a space, the correct form is for example
'-u=cylinders'.
-C, --cylinders number
Specify the number of cylinders of the disk. I have no idea
why anybody would want to do so.
-H, --heads number
Specify the number of heads of the disk. (Not the physical
number, of course, but the number used for partition tables.)
Reasonable values are 255 and 16.
-S, --sectors number
Specify the number of sectors per track of the disk. (Not the
physical number, of course, but the number used for partition
tables.) A reasonable value is 63.
-w, --wipe when
Wipe filesystem, RAID and partition-table signatures from the
device, in order to avoid possible collisions. The argument
when can be auto, never or always. When this option is not
given, the default is auto, in which case signatures are wiped
only when in interactive mode. In all cases detected
signatures are reported by warning messages before a new
partition table is created. See also wipefs(8) command.
-W, --wipe-partitions when
Wipe filesystem, RAID and partition-table signatures from a
newly created partitions, in order to avoid possible
collisions. The argument when can be auto, never or always.
When this option is not given, the default is auto, in which
case signatures are wiped only when in interactive mode and
after confirmation by user. In all cases detected signatures
are reported by warning messages before a new partition is
created. See also wipefs(8) command.
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
The device is usually /dev/sda, /dev/sdb or so. A device name
refers to the entire disk. Old systems without libata (a library
used inside the Linux kernel to support ATA host controllers and
devices) make a difference between IDE and SCSI disks. In such
cases the device name will be /dev/hd* (IDE) or /dev/sd* (SCSI).
The partition is a device name followed by a partition number. For
example, /dev/sda1 is the first partition on the first hard disk
in the system. See also Linux kernel documentation (the
Documentation/admin-guide/devices.txt file).
The "last sector" dialog accepts partition size specified by
number of sectors or by +/-<size>{K,B,M,G,...} notation.
If the size is prefixed by '+' then it is interpreted as relative
to the partition first sector. If the size is prefixed by '-' then
it is interpreted as relative to the high limit (last available
sector for the partition).
In the case the size is specified in bytes, then the number may be
followed by the multiplicative suffixes KiB (1024 bytes), MiB
(1024*1024 bytes), and so on for GiB, TiB, PiB, EiB, ZiB and YiB.
The "iB" is optional, e.g., "K" has the same meaning as "KiB".
The relative sizes if specified with multiplicative suffixes (e.g.
+100MiB) are always aligned according to device I/O limits. The
+/-<size>{K,B,M,G,...} notation is recommended.
The last sector of the partition is strictly calculated as <start>
+ <size> (without -1) if the size is specified by the +<sectors>
notation. In this case, the size is not aligned to the device I/O
limits.
For backward compatibility fdisk also accepts the suffixes KB
(1000 bytes), MB (1000*1000 bytes), and so on for GB, TB, PB, EB,
ZB and YB. These 10^N suffixes are deprecated.
fdisk allows reading (by 'I' command) sfdisk(8) compatible script
files. The script is applied to in-memory partition table, and
then it is possible to modify the partition table before you write
it to the device.
And vice-versa it is possible to write the current in-memory disk
layout to the script file by command 'O'.
The script files are compatible between cfdisk(8), sfdisk(8),
fdisk and other libfdisk applications. For more details see
sfdisk(8).
GPT (GUID Partition Table)
GPT is modern standard for the layout of the partition table.
GPT uses 64-bit logical block addresses, checksums, UUIDs and
names for partitions and an unlimited number of partitions
(although the number of partitions is usually restricted to
128 in many partitioning tools).
Note that the first sector is still reserved for a protective
MBR in the GPT specification. It prevents MBR-only
partitioning tools from mis-recognizing and overwriting GPT
disks.
GPT is always a better choice than MBR, especially on modern
hardware with a UEFI boot loader.
DOS-type (MBR)
A DOS-type partition table can describe an unlimited number of
partitions. In sector 0 there is room for the description of 4
partitions (called `primary'). One of these may be an extended
partition; this is a box holding logical partitions, with
descriptors found in a linked list of sectors, each preceding
the corresponding logical partitions. The four primary
partitions, present or not, get numbers 1-4. Logical
partitions are numbered starting from 5.
In a DOS-type partition table the starting offset and the size
of each partition is stored in two ways: as an absolute number
of sectors (given in 32 bits), and as a
Cylinders/Heads/Sectors triple (given in 10+8+6 bits). The
former is OK — with 512-byte sectors this will work up to 2
TB. The latter has two problems. First, these C/H/S fields can
be filled only when the number of heads and the number of
sectors per track are known. And second, even if we know what
these numbers should be, the 24 bits that are available do not
suffice. DOS uses C/H/S only, Windows uses both, Linux never
uses C/H/S. The C/H/S addressing is deprecated and may be
unsupported in some later fdisk version.
Please, read the DOS-mode section if you want DOS-compatible
partitions. fdisk does not care about cylinder boundaries by
default.
BSD/Sun-type
A BSD/Sun disklabel can describe 8 partitions, the third of
which should be a `whole disk' partition. Do not start a
partition that actually uses its first sector (like a swap
partition) at cylinder 0, since that will destroy the
disklabel. Note that a BSD label is usually nested within a
DOS partition.
IRIX/SGI-type
An IRIX/SGI disklabel can describe 16 partitions, the eleventh
of which should be an entire `volume' partition, while the
ninth should be labeled `volume header'. The volume header
will also cover the partition table, i.e., it starts at block
zero and extends by default over five cylinders. The remaining
space in the volume header may be used by header directory
entries. No partitions may overlap with the volume header.
Also do not change its type or make some filesystem on it,
since you will lose the partition table. Use this type of
label only when working with Linux on IRIX/SGI machines or
IRIX/SGI disks under Linux.
A sync(2) and an ioctl(BLKRRPART) (rereading the partition
table from disk) are performed before exiting when the
partition table has been updated.
Note that all this is deprecated. You don’t have to care about
things like geometry and cylinders on modern operating systems. If
you really want DOS-compatible partitioning then you have to
enable DOS mode and cylinder units by using the '-c=dos
-u=cylinders' fdisk command-line options.
The DOS 6.x FORMAT command looks for some information in the first
sector of the data area of the partition, and treats this
information as more reliable than the information in the partition
table. DOS FORMAT expects DOS FDISK to clear the first 512 bytes
of the data area of a partition whenever a size change occurs. DOS
FORMAT will look at this extra information even if the /U flag is
given — we consider this a bug in DOS FORMAT and DOS FDISK.
The bottom line is that if you use fdisk or cfdisk(8) to change
the size of a DOS partition table entry, then you must also use
dd(1) to zero the first 512 bytes of that partition before using
DOS FORMAT to format the partition. For example, if you were using
fdisk to make a DOS partition table entry for /dev/sda1, then
(after exiting fdisk and rebooting Linux so that the partition
table information is valid) you would use the command dd
if=/dev/zero of=/dev/sda1 bs=512 count=1 to zero the first 512
bytes of the partition.
fdisk usually obtains the disk geometry automatically. This is not
necessarily the physical disk geometry (indeed, modern disks do
not really have anything like a physical geometry, certainly not
something that can be described in the simplistic
Cylinders/Heads/Sectors form), but it is the disk geometry that
MS-DOS uses for the partition table.
Usually all goes well by default, and there are no problems if
Linux is the only system on the disk. However, if the disk has to
be shared with other operating systems, it is often a good idea to
let an fdisk from another operating system make at least one
partition. When Linux boots it looks at the partition table, and
tries to deduce what (fake) geometry is required for good
cooperation with other systems.
Whenever a partition table is printed out in DOS mode, a
consistency check is performed on the partition table entries.
This check verifies that the physical and logical start and end
points are identical, and that each partition starts and ends on a
cylinder boundary (except for the first partition).
Some versions of MS-DOS create a first partition which does not
begin on a cylinder boundary, but on sector 2 of the first
cylinder. Partitions beginning in cylinder 1 cannot begin on a
cylinder boundary, but this is unlikely to cause difficulty unless
you have OS/2 on your machine.
For best results, you should always use an OS-specific partition
table program. For example, you should make DOS partitions with
the DOS FDISK program and Linux partitions with the Linux fdisk or
Linux cfdisk(8) programs.
The output colorization is implemented by terminal-colors.d(5)
functionality. Implicit coloring can be disabled by an empty file
/etc/terminal-colors.d/fdisk.disable
for the fdisk command or for all tools by
/etc/terminal-colors.d/disable
Since version 2.41, the $NO_COLOR environment variable is also
supported to disable output colorization unless explicitly enabled
by a command-line option.
The user-specific $XDG_CONFIG_HOME/terminal-colors.d or
$HOME/.config/terminal-colors.d overrides the global setting.
Note that the output colorization may be enabled by default, and
in this case terminal-colors.d directories do not have to exist
yet.
The logical color names supported by fdisk are:
header
The header of the output tables.
help-title
The help section titles.
warn
The warning messages.
welcome
The welcome message.
FDISK_DEBUG=all
enables fdisk debug output.
LIBFDISK_DEBUG=all
enables libfdisk debug output.
LIBBLKID_DEBUG=all
enables libblkid debug output.
LIBSMARTCOLS_DEBUG=all
enables libsmartcols debug output.
LIBSMARTCOLS_DEBUG_PADDING=on
use visible padding characters.
LOCK_BLOCK_DEVICE=<mode>
use exclusive BSD lock. The mode is "1" or "0". See --lock for
more details.
Karel Zak <[email protected]>, Davidlohr Bueso <[email protected]>
The original version was written by Andries E. Brouwer, A. V. Le
Blanc and others.
cfdisk(8), mkfs(8), partx(8), sfdisk(8)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The fdisk command is part of the util-linux package which can be
downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) If you discover any
rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to [email protected]
util-linux 2.42-start-521-ec46 2025-08-09 FDISK(8)
Pages that refer to this page: systemd-dissect(1), addpart(8), btrfs-filesystem(8), cfdisk(8), delpart(8), mkswap(8), parted(8), partx(8), resize2fs(8), resizepart(8), sfdisk(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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