bionic (8) fdisk.8.gz

Provided by: fdisk_2.31.1-0.4ubuntu3.7_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 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.

       -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.

       -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-partition 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/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.

       LIBSMARTCOLS_DEBUG_PADDING=on
              use visible padding characters. Requires enabled LIBSMARTCOLS_DEBUG.

SEE ALSO

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

AVAILABILITY

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