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FDISK(8)                              System Administration                              FDISK(8)

       fdisk - manipulate disk partition table

       fdisk [options] device

       fdisk -l [device...]

       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 divi‐
       sion  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 guaran‐
       teed.  The input (the commands) should always be backward compatible.

       -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 sector‐

       -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 argu‐
              ment -- 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 in interactive mode.  The optional argument when can be auto,
              never or always.  The default is auto.

       -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.

       -s, --getsz
              Print the size in 512-byte sectors of each given block device.  This option is DEP‐
              RECATED 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.

       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  documen‐
       tation (the Documentation/devices.txt file).

       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.

       GPT (GUID Partition Table)
              GPT is modern standard for the layout of the partition table.  GPT uses 64-bit log‐
              ical 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 speci‐
              fication.   It  prevents MBR-only partitioning tools from mis-recognizing and over‐
              writing 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 sec‐
              tor 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.

              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 sec‐
              tor  (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 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

       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 physi‐
       cal disk geometry (indeed, modern disks do not really have anything like a physical geome‐
       try,  certainly not something that can be described in the simplistic Cylinders/Heads/Sec‐
       tors 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 bound‐
       ary, 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 exam‐
       ple,  you  should make DOS partitions with the DOS FDISK program and Linux partitions with
       the Linux fdisk or Linux cfdisk programs.

       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.

              The help section titles.

       warn   The warning messages.

              The welcome message.

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

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

       Setting LIBFDISK_DEBUG=0xffff enables debug output.

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

       The  fdisk  command is part of the util-linux package and is available from ftp://ftp.ker‐

util-linux                                September 2013                                 FDISK(8)

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