fdisk(8) — Linux manual page


FDISK(8)                    System Administration                   FDISK(8)

NAME         top

       fdisk - manipulate disk partition table

SYNOPSIS         top

       fdisk [options] device

       fdisk -l [device...]

DESCRIPTION         top

       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>" advices 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.

OPTIONS         top

       -b, --sector-size sectorsize
              Specify the sector size of the disk.  Valid values are 512,
              1024, 2048, and 4096.  (Recent kernels know the sector size.
              Use this option only on old kernels or to override the
              kernel's ideas.)  Since util-linux-2.17, fdisk differentiates
              between logical and physical sector size.  This option changes
              both sector sizes to 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'.

       -h, --help
              Display a help text and exit.

       -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, those mentioned in
              /proc/partitions (if that file exists) are used.

       -x, --list-details
              Like --list, but provides more details.

              Use exclusive BSD lock for device or file it operates.  The
              optional argument mode can be yes, no (or 1 and 0) or
              nonblock.  If the mode argument is omitted, it defaults to
              "yes".  This option overwrites environment variable
              $LOCK_BLOCK_DEVICE.  The default is not to use any lock at
              all, but it's recommended to avoid collisions with udevd 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

       -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.

       -V, --version
              Display version information and exit.

DEVICES         top

       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).

SIZES         top

       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 than the number may be
       followed by the multiplicative suffixes KiB=1024, MiB=1024*1024, 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 are always aligned according to device I/O limits.
       The +/-<size>{K,B,M,G,...} notation is recommended.

       For backward compatibility fdisk also accepts the suffixes KB=1000,
       MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. These 10^N
       suffixes are deprecated.

SCRIPT FILES         top

       fdisk allows reading (by 'I' command) sfdisk 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

       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, sfdisk, fdisk and
       other libfdisk applications. For more details see sfdisk(8).

DISK LABELS         top

       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

              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

              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.

              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() and an ioctl(BLKRRPART) (rereading the partition table from
       disk) are performed before exiting when the partition table has been

DOS mode and DOS 6.x WARNING         top

       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 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

       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 programs.

COLORS         top

       Implicit coloring can be disabled by an empty file /etc/terminal-

       See terminal-colors.d(5) for more details about colorization
       configuration. The logical color names supported by fdisk are:

       header The header of the output tables.

              The help section titles.

       warn   The warning messages.

              The welcome message.

ENVIRONMENT         top

              enables fdisk debug output.

              enables libfdisk debug output.

              enables libblkid debug output.

              enables libsmartcols debug output.

              use visible padding characters. Requires enabled

              use exclusive BSD lock.  The mode is "1" or "0".  See --lock
              for more details.

AUTHORS         top

       Karel Zak ⟨kzak@redhat.com⟩
       Davidlohr Bueso ⟨dave@gnu.org⟩

       The original version was written by Andries E. Brouwer, A. V. Le
       Blanc and others.

SEE ALSO         top

       cfdisk(8), mkfs(8), partx(8), sfdisk(8)

AVAILABILITY         top

       The fdisk command is part of the util-linux package and is available
       from https://www.kernel.org/pub/linux/utils/util-linux/.

COLOPHON         top

       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
       util-linux@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
       2020-11-01.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-10-21.)  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

util-linux                      February 2016                       FDISK(8)

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