Provided by: util-linux_2.27.1-6ubuntu3_amd64 bug

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.

       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 begin of the first disk sector when create 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 --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.

       -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(1).

       -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.

       -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/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. In this case the size is expected in bytes and 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 to read (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 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,  sfdisk,  fdisk and another 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 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.

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.

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.

SEE ALSO

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

AVAILABILITY

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