fdisk

FDISK(8)                      System Administration                     FDISK(8)



NAME
       fdisk - manipulate disk partition table

SYNOPSIS
       fdisk [options] device

       fdisk -l [device...]

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

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

AVAILABILITY
       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/>.



util-linux 2.37.2                  2021-08-16                           FDISK(8)