fdisk(8) — Linux manual page

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

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, 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 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
           '*-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.

       -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(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).

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

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 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.

COLORS         top

       Implicit coloring can be disabled by an empty file
       /etc/terminal-colors.d/fdisk.disable.

       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.

       help-title
           The help section titles.

       warn
           The warning messages.

       welcome
           The welcome message.

ENVIRONMENT         top

       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.

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)

REPORTING BUGS         top

       For bug reports, use the issue tracker at
       https://github.com/karelzak/util-linux/issues.

AVAILABILITY         top

       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
       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
       2021-08-27. (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-24.) 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 man-pages@man7.org

util-linux 2.37.294-0c7e       2021-08-19                       FDISK(8)

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