SYNOPSIS

       fdisk-linux [-u] [-b sectorsize] [-C cyls] [-H heads] [-S sects] device

       fdisk-linux -l [-u] [device ...]

       fdisk-linux -s partition ...

       fdisk-linux -v

DESCRIPTION

       Hard disks can be divided into one or more logical disks called  parti-
       tions.  This division is described in the partition table found in sec-
       tor 0 of the disk.

       In the BSD world one talks about `disk slices' and a `disklabel'.

       Linux needs at least one partition, namely for its  root  file  system.
       It  can  use swap files and/or swap partitions, but the latter are more
       efficient. So, usually one will want a second Linux partition dedicated
       as  swap  partition.  On Intel compatible hardware, the BIOS that boots
       the system can often only access the first 1024 cylinders of the  disk.
       For this reason people with large disks often create a third partition,
       just a few MB large, typically mounted on /boot, to  store  the  kernel
       image and a few auxiliary files needed at boot time, so as to make sure
       that this stuff is accessible to the BIOS.  There  may  be  reasons  of
       security,  ease  of  administration and backup, or testing, to use more
       than the minimum number of partitions.

       fdisk (in the first form of invocation) is a menu  driven  program  for
       creation and manipulation of partition tables.  It understands DOS type
       partition tables and BSD or SUN type disklabels.

       The device is usually one of the following:
              /dev/ad0
              /dev/ad1
              /dev/da0
              /dev/da1
       (/dev/adN for IDE disks, /dev/daN for SCSI disks, N=0,1,2...)  A device
       name refers to the entire disk.

       The  partition is a device name followed by 's' and a partition number.
       For example, /dev/ad0s1 is the first partition on the  first  IDE  hard
       disk in the system.

       A  BSD/SUN type 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.

       An IRIX/SGI type 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  parti-
       partitions start numbering 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 different problems. First of all, these
       C/H/S fields can be filled only when the number of heads and the number
       of  sectors  per  track are known. Secondly, 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.

       If  possible,  fdisk will obtain 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 some-
       thing that  can  be  described  in  simplistic  Cylinders/Heads/Sectors
       form),  but is the disk geometry that MS-DOS uses for the partition ta-
       ble.

       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) geome-
       try is required for good cooperation with other systems.

       Whenever  a partition table is printed out, a consistency check is per-
       formed on the partition table entries.  This check  verifies  that  the
       physical  and  logical start and end points are identical, and that the
       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.   Parti-
       tions  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.

       A  sync() and a sys_bsd_ptsync() (reread partition table from disk) are
       performed before exiting when the partition  table  has  been  updated.
       Long  ago  it used to be necessary to reboot after the use of fdisk.  I
       do not think this is the case anymore - indeed, rebooting  too  quickly
       might cause loss of not-yet-written data. Note that both the kernel and
       the disk hardware may buffer data.

DOS 6.x WARNING

       The DOS 6.x FORMAT command looks for some information in the first sec-
       tor  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

       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
       program.

OPTIONS

       -b sectorsize
              Specify the sector size of the disk. Valid values are 512, 1024,
              or 2048.  (Recent kernels know the sector size. Use this only on
              old kernels or to override the kernel's ideas.)

       -C cyls
              Specify the number of cylinders of the disk.  I have no idea why
              anybody would want to do so.

       -H heads
              Specify the number of heads of the disk. (Not the physical  num-
              ber, of course, but the number used for partition tables.)  Rea-
              sonable values are 255 and 16.

       -S sects
              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.

       -l     List the partition tables for the  specified  devices  and  then
              exit.   If no devices are given, those mentioned in /proc/parti-
              tions (if that exists) are used.

       -u     When listing partition tables, give sizes in sectors instead  of
              cylinders.

       -s partition
              The size of the partition (in blocks) is printed on the standard
              output.

       -v     Print version number of fdisk program and exit.

BUGS

       There are several *fdisk programs around.  Each has  its  problems  and
       strengths.   Try  them  in  the  order cfdisk, fdisk, sfdisk.  (Indeed,
       cfdisk is a beautiful program that has strict requirements on the  par-
       tition  tables  it accepts, and produces high quality partition tables.
       Use it if you can.  fdisk is a buggy program that does fuzzy  things  -
       usually  it happens to produce reasonable results. Its single advantage
       is that it has some support for BSD disk labels and other non-DOS  par-
       tition  tables.  Avoid it if you can.  sfdisk is for hackers only - the
       user interface is terrible, but it is more correct than fdisk and  more
       powerful  than  both fdisk and cfdisk.  Moreover, it can be used nonin-
       teractively.)