Provided by: util-linux_2.20.1-1ubuntu3_amd64 bug

NAME

       sfdisk - partition table manipulator for Linux

SYNOPSIS

       sfdisk [options] device
       sfdisk -s [partition]

DESCRIPTION

       sfdisk  has  four  (main)  uses:  list  the  size of a partition, list the partitions on a
       device, check the partitions on a device, and - very dangerous - repartition a device.

       sfdisk doesn't understand the GUID Partition Table (GPT) format and it is not designed for
       large partitions.  In these cases use the more advanced GNU parted(8).

   List sizes
       sfdisk  -s  partition  gives  the  size  of  partition  in  blocks.  This may be useful in
       connection with programs  like  mkswap(8).   Here  partition  is  usually  something  like
       /dev/hda1 or /dev/sdb12, but may also be an entire disk, like /dev/xda.

              % sfdisk -s /dev/hda9
              81599

       If  the  partition  argument  is omitted, sfdisk will list the sizes of all disks, and the
       total:

              % sfdisk -s
              /dev/hda: 208896
              /dev/hdb: 1025136
              /dev/hdc: 1031063
              /dev/sda: 8877895
              /dev/sdb: 1758927
              total: 12901917 blocks

   List partitions
       The second type of invocation: sfdisk -l device will list the partitions on the  specified
       device.  If the device argument is omitted, the partitions on all hard disks are listed.

              % sfdisk -l /dev/hdc

              Disk /dev/hdc: 16 heads, 63 sectors, 2045 cylinders
              Units = cylinders of 516096 bytes, blocks of 1024 bytes, counting from 0

                 Device Boot Start     End   #cyls   #blocks   Id  System
              /dev/hdc1          0+    406     407-   205096+  83  Linux native
              /dev/hdc2        407     813     407    205128   83  Linux native
              /dev/hdc3        814    2044    1231    620424   83  Linux native
              /dev/hdc4          0       -       0         0    0  Empty

       The  trailing  -  and  + signs indicate that rounding has taken place, and that the actual
       value is slightly less or more.  To see the exact values, ask for a listing  with  sectors
       as unit (-u S).

   Check partitions
       The  third  type  of invocation: sfdisk -V device will apply various consistency checks to
       the partition tables on device.  It prints `OK' or complains.  The -V option can  be  used
       together  with -l.  In a shell script one might use sfdisk -V -q device which only returns
       a status.

   Create partitions
       The fourth type of invocation: sfdisk device will cause sfdisk to read  the  specification
       for  the  desired  partitioning  of  device  from  standard  input, and then to change the
       partition tables on that disk.  Thus it is possible to use sfdisk  from  a  shell  script.
       When  sfdisk  determines that its standard input is a terminal, it will be conversational;
       otherwise it will abort on any error.

       BE EXTREMELY CAREFUL - ONE TYPING MISTAKE AND ALL YOUR DATA IS LOST

       As a precaution, one can save the sectors changed by sfdisk:

              % sfdisk /dev/hdd -O hdd-partition-sectors.save
              ...

       Then, if you discover that you did something stupid before anything else has been  written
       to disk, it may be possible to recover the old situation with:

              % sfdisk /dev/hdd -I hdd-partition-sectors.save

       (This  is  not  the  same as saving the old partition table: a readable version of the old
       partition table can be saved  using  the  -d  option.   However,  if  you  create  logical
       partitions, the sectors describing them are located somewhere on disk, possibly on sectors
       that were not part of the partition table before.  Thus, the  information  the  -O  option
       saves is not a binary version of the output of -d.)

       There are many options.

OPTIONS

       -v, --version
              Print version number of sfdisk and exit immediately.

       -h, --help
              Print a usage message and exit immediately.

       -T, --list-types
              Print the recognized types (system Id's).

       -s, --show-size
              List the size of a partition.

       -g, --show-geometry
              List the kernel's idea of the geometry of the indicated disk(s).

       -G, --show-pt-geometry
              List the geometry of the indicated disks guessed by looking at the partition table.

       -l, --list
              List the partitions of a device.

       -d, --dump
              Dump  the  partitions  of  a  device  in  a  format  that  is  usable  as  input to
              /fBsfdisk/fR.  For example,
                  % sfdisk -d /dev/hda > hda.out
                  % sfdisk /dev/hda < hda.out
              will correct the bad last extended partition that the OS/2 fdisk creates.

       -V, --verify
              Test whether partitions seem correct.  (See the third invocation type above.)

       -i, --increment
              Number cylinders etc. starting from 1 instead of 0.

       -N number
              Change only the single partition indicated.  For example:
                  % sfdisk /dev/hdb -N5
                  ,,,*
              will make the fifth partition on /dev/hdb bootable (`active')  and  change  nothing
              else.  (Probably this fifth partition is called /dev/hdb5, but you are free to call
              it something else, like `/my_equipment/disks/2/5' or so).

       -A, --activate number
              Make the indicated partition(s) active, and all others inactive.

       -c, --id number [Id]
              If no Id argument given: print the partition Id of the indicated partition.  If  an
              Id  argument  is  present:  change  the type (Id) of the indicated partition to the
              given value.  This option has two longer forms, --print-id  and  --change-id.   For
              example:
                  % sfdisk --print-id /dev/hdb 5
                  6
                  % sfdisk --change-id /dev/hdb 5 83
                  OK
              first reports that /dev/hdb5 has Id 6, and then changes that into 83.

       -u, --unit letter
              Interpret  the  input  and  show the output in the units specified by letter.  This
              letter can be one of  S,  C,  B  or  M,  meaning  Sectors,  Cylinders,  Blocks  and
              Megabytes,  respectively.   The default is cylinders, at least when the geometry is
              known.

       -x, --show-extended
              Also list non-primary extended partitions on output,  and  expect  descriptors  for
              them on input.

       -C, --cylinders cylinders
              Specify the number of cylinders, possibly overriding what the kernel thinks.

       -H, --heads heads
              Specify the number of heads, possibly overriding what the kernel thinks.

       -S, --sectors sectors
              Specify the number of sectors, possibly overriding what the kernel thinks.

       -f, --force
              Do what I say, even if it is stupid.

       -q, --quiet
              Suppress warning messages.

       -L, --Linux
              Do not complain about things irrelevant for Linux.

       -D, --DOS
              For  DOS-compatibility:  waste  a  little  space.   (More precisely: if a partition
              cannot contain sector 0, e.g. because that is the MBR of the  device,  or  contains
              the  partition  table of an extended partition, then sfdisk would make it start the
              next sector.  However, when this option is given it skips to the start of the  next
              track,  wasting  for  example  33  sectors (in case of 34 sectors/track), just like
              certain versions of DOS do.)  Certain Disk Managers and boot loaders (such as OSBS,
              but  not LILO or the OS/2 Boot Manager) also live in this empty space, so maybe you
              want this option if you use one.

       -E, --DOS-extended
              Take the starting sector numbers of "inner" extended partitions to be  relative  to
              the  starting  cylinder  boundary  of the outer one (like some versions of DOS do),
              rather than relative to the actual starting sector (like Linux  does).   (The  fact
              that  there  is  a  difference  here  means  that  one  should  always let extended
              partitions start at cylinder boundaries if  DOS  and  Linux  should  interpret  the
              partition  table  in  the  same  way.   Of  course one can only know where cylinder
              boundaries are when one knows what geometry DOS will use for this disk.)

       --IBM, --leave-last
              Certain IBM diagnostic programs assume that they can use the  last  cylinder  on  a
              disk for disk-testing purposes.  If you think you might ever run such programs, use
              this option to  tell  sfdisk  that  it  should  not  allocate  the  last  cylinder.
              Sometimes the last cylinder contains a bad sector table.

       -n     Go through all the motions, but do not actually write to disk.

       -R, --re-read
              Only  execute the BLKRRPART ioctl (to make the kernel re-read the partition table).
              This can be useful for checking  in  advance  that  the  final  BLKRRPART  will  be
              successful, and also when you changed the partition table `by hand' (e.g., using dd
              from a backup).  If the kernel complains (`device busy for  revalidation  (usage  =
              2)')  then something still uses the device, and you still have to unmount some file
              system, or say swapoff to some swap partition.

       --no-reread
              When starting a repartitioning of a disk, sfdisk  checks  that  this  disk  is  not
              mounted, or in use as a swap device, and refuses to continue if it is.  This option
              suppresses the test.  (On the other hand, the  -f  option  would  force  sfdisk  to
              continue even when this test fails.)

       --in-order
              Caution, see warning section.  To be documented.

       --not-in-order
              Caution, see warning section.  To be documented.

       --inside-outer
              Caution, see warning section.  Chaining order.

       --not-inside-outer
              Caution, see warning section.  Chaining order.

       --nested
              Caution,  see  warning  section.   Every  partition is contained in the surrounding
              partitions and is disjoint from all others.

       --chained
              Caution, see warning section.  Every data partition is contained in the surrounding
              partitions  and  disjoint  from all others, but extended partitions may lie outside
              (insofar as allowed by all_logicals_inside_outermost_extended).

       --onesector
              Caution, see warning section.  All data partitions are mutually disjoint;  extended
              partitions each use one sector only (except perhaps for the outermost one).

       -O file
              Just  before  writing  the  new  partition, output the sectors that are going to be
              overwritten to file (where hopefully file resides on another disk, or on a floppy).

       -I file
              After destroying your filesystems with an unfortunate  sfdisk  command,  you  would
              have  been able to restore the old situation if only you had preserved it using the
              -O flag.

THEORY

       Block 0 of a disk (the Master Boot Record) contains  among  other  things  four  partition
       descriptors. The partitions described here are called primary partitions.

       A partition descriptor has 6 fields:
              struct partition {
                  unsigned char bootable;        /* 0 or 0x80 */
                  hsc begin_hsc;
                  unsigned char id;
                  hsc end_hsc;
                  unsigned int starting_sector;
                  unsigned int nr_of_sectors;
              }

       The  two  hsc  fields  indicate  head, sector and cylinder of the begin and the end of the
       partition. Since each hsc field only takes 3 bytes, only 24 bits are available, which does
       not  suffice  for big disks (say > 8GB). In fact, due to the wasteful representation (that
       uses a byte for the number of heads, which is typically 16), problems already  start  with
       0.5GB.  However Linux does not use these fields, and problems can arise only at boot time,
       before Linux has been started. For more details, see the lilo documentation.

       Each partition has a type, its `Id', and if this type is 5 or f (`extended partition') the
       starting  sector  of the partition again contains 4 partition descriptors. MSDOS only uses
       the first two of these: the first one an actual data partition, and the second  one  again
       an  extended  partition  (or empty).  In this way one gets a chain of extended partitions.
       Other operating systems have slightly different conventions.  Linux also accepts  type  85
       as  equivalent  to  5  and f - this can be useful if one wants to have extended partitions
       under Linux past the 1024 cylinder boundary, without DOS FDISK hanging.  (If there  is  no
       good reason, you should just use 5, which is understood by other systems.)

       Partitions  that  are  not primary or extended are called logical.  Often, one cannot boot
       from logical partitions (because the process of finding them is more  involved  than  just
       looking  at  the  MBR).   Note that of an extended partition only the Id and the start are
       used. There are various conventions about what to write in the other  fields.  One  should
       not try to use extended partitions for data storage or swap.

INPUT FORMAT

       sfdisk reads lines of the form
              <start> <size> <id> <bootable> <c,h,s> <c,h,s>
       where each line fills one partition descriptor.

       Fields are separated by whitespace, or comma or semicolon possibly followed by whitespace;
       initial and trailing whitespace is ignored.  Numbers can be octal, decimal or hexadecimal,
       decimal is default.  When a field is absent or empty, a default value is used.

       The <c,h,s> parts can (and probably should) be omitted - sfdisk computes them from <start>
       and <size> and the disk geometry as given by the kernel or specified using the -H, -S,  -C
       flags.

       Bootable is specified as [*|-], with as default not-bootable.  (The value of this field is
       irrelevant for Linux - when Linux runs it has been booted already - but might play a  role
       for  certain  boot  loaders  and for other operating systems.  For example, when there are
       several primary DOS partitions, DOS assigns C: to the first among these that is bootable.)

       Id is given in hex, without the 0x prefix, or is [E|S|L|X], where L (LINUX_NATIVE (83)) is
       the  default,  S  is LINUX_SWAP (82), E is EXTENDED_PARTITION (5), and X is LINUX_EXTENDED
       (85).

       The default value of start is the first nonassigned sector/cylinder/...

       The default value of size is as much as possible (until next partition or end-of-disk).

       However, for the four partitions inside an extended partition,  the  defaults  are:  Linux
       partition, Extended partition, Empty, Empty.

       But  when  the  -N  option (change a single partition only) is given, the default for each
       field is its previous value.

       A '+' can be specified instead of a number for size, which means as much as possible. This
       is useful with the -N option.

EXAMPLE

       The command
              sfdisk /dev/hdc << EOF
              0,407
              ,407
              ;
              ;
              EOF
       will partition /dev/hdc just as indicated above.

       The command
              sfdisk /dev/hdb << EOF
              ,3,L
              ,60,L
              ,19,S
              ,,E
              ,130,L
              ,130,L
              ,130,L
              ,,L
              EOF
       will  partition  /dev/hdb into two Linux partitions of 3 and 60 cylinders, a swap space of
       19 cylinders, and an extended partition covering the rest. Inside the  extended  partition
       there are four Linux logical partitions, three of 130 cylinders and one covering the rest.

       With  the  -x  option, the number of input lines must be a multiple of 4: you have to list
       the two empty partitions that you never want using two blank lines. Without the -x option,
       you  give  one  line  for the partitions inside a extended partition, instead of four, and
       terminate with end-of-file (^D).  (And sfdisk will assume that your input line  represents
       the first of four, that the second one is extended, and the 3rd and 4th are empty.)

CAUTION WARNINGS

       The  options  marked  with  caution in the manual page are dangerous.  For example not all
       functionality is completely implemented, which can be a reason for unexpected results.

DOS 6.x WARNING

       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 sfdisk to change the size of a DOS partition table
       entry, then you must also use dd to zero the first 512  bytes  of  that  partition  before
       using DOS FORMAT to format the partition.  For example, if you were using sfdisk to make a
       DOS partition table entry for /dev/hda1, then (after exiting sfdisk and rebooting Linux so
       that  the partition table information is valid) you would use the command "dd if=/dev/zero
       of=/dev/hda1 bs=512 count=1" to zero the first 512 bytes of the partition.   BE  EXTREMELY
       CAREFUL  if  you  use  the dd command, since a small typo can make all of the data on your
       disk useless.

       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 sfdisk program.

DRDOS WARNINGS

       Stephen Tweedie reported (930515): `Most reports of superblock corruption turn out  to  be
       due  to  bad  partitioning,  with  one  filesystem  overrunning  the start of the next and
       corrupting its superblock.  I have even had  this  problem  with  the  supposedly-reliable
       DRDOS.   This  was  quite  possibly  due to DRDOS-6.0's FDISK command.  Unless I created a
       blank track or cylinder between the DRDOS partition and  the  immediately  following  one,
       DRDOS  would happily stamp all over the start of the next partition.  Mind you, as long as
       I keep a little free disk space after any DRDOS partition, I don't have any other problems
       with the two coexisting on the one drive.'

       A.  V.  Le  Blanc  writes in README.efdisk: `Dr. DOS 5.0 and 6.0 has been reported to have
       problems cooperating with Linux, and with this version  of  efdisk  in  particular.   This
       efdisk  sets  the  system  type  to  hexadecimal  81.   Dr. DOS seems to confuse this with
       hexadecimal 1, a DOS code.  If you use Dr. DOS, use the efdisk command 't' to  change  the
       system  code of any Linux partitions to some number less than hexadecimal 80; I suggest 41
       and 42 for the moment.'

       A. V. Le Blanc writes in his README.fdisk: `DR-DOS  5.0  and  6.0  are  reported  to  have
       difficulties  with  partition  ID  codes of 80 or more.  The Linux `fdisk' used to set the
       system type of new partitions to hexadecimal  81.   DR-DOS  seems  to  confuse  this  with
       hexadecimal  1,  a  DOS  code.   The values 82 for swap and 83 for file systems should not
       cause problems with DR-DOS.  If they do, you may use the `fdisk' command `t' to change the
       system  code of any Linux partitions to some number less than hexadecimal 80; I suggest 42
       and 43 for the moment.'

       In fact, it seems that only 4 bits are significant  for  the  DRDOS  FDISK,  so  that  for
       example 11 and 21 are listed as DOS 2.0. However, DRDOS itself seems to use the full byte.
       I have not been able to reproduce any corruption with DRDOS or its fdisk.

BUGS

       There are too many options.

       There is no support for non-DOS partition types.

SEE ALSO

       cfdisk(8), fdisk(8), mkfs(8), parted(8), partprobe(8), kpartx(8)

AVAILABILITY

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