CFDISK(8)           Linux Programmer's Manual           CFDISK(8)

NAME
       cfdisk - Curses based disk partition table manipulator for
       Linux

SYNOPSIS
       cfdisk [ -avz ] [ -c cylinders ] [ -h heads ]  [  -s  sec-
       tors-per-track ] [ -P opt ] [ device ]

DESCRIPTION
       cfdisk  is  a curses based program for partitioning a hard
       disk drive.  The device can be any one of the following:

              /dev/hda [default]
              /dev/hdb
              /dev/sda
              /dev/sdb
              /dev/sdc
              /dev/sdd

       cfdisk first tries to read the geometry of the hard  disk.
       If  it  fails,  an  error  message is displayed and cfdisk
       exits.  This should only happen when partitioning  a  SCSI
       drive on an adapter without a BIOS.  To correct this prob-
       lem, you can set the  cylinders,  heads  and  sectors-per-
       track on the command line.  Next, cfdisk tries to read the
       current partition table from the disk  drive.   If  it  is
       unable to figure out the partition table, an error is dis-
       played and the program will  exit.   This  might  also  be
       caused by incorrect geometry information, and can be over-
       ridden on the command line.  Another way around this prob-
       lem is with the -z option.  This will ignore the partition
       table on the disk.

       The main display is composed of four sections, from top to
       bottom: the header, the partitions, the command line and a
       warning line.  The header contains the  program  name  and
       version  number  followed by the disk drive and its geome-
       try.  The partitions section always displays  the  current
       partition table.  The command line is the place where com-
       mands and text are entered.  The  available  commands  are
       usually  displayed  in brackets.  The warning line is usu-
       ally empty except when there is important  information  to
       be  displayed.   The current partition is highlighted with
       reverse video (or an arrow if the  -a  option  is  given).
       All  partition specific commands apply to the current par-
       tition.

       The format of the partition table in the  partitions  sec-
       tion  is, from left to right: Name, Flags, Partition Type,
       Filesystem Type and  Size.   The  name  is  the  partition
       device  name.   The  flags can be Boot, which designates a
       bootable partition or NC, which stands for "Not Compatible
       with DOS or OS/2".  DOS, OS/2 and possibly other operating
       systems require the first sector of the first partition on
       the disk and all logical partitions to begin on the second
       head.  This wastes the second through the last  sector  of
       the  first  track  of  the first head (the first sector is
       taken by the partition table itself).  cfdisk  allows  you
       to  recover these "lost" sectors with the maximize command
       (m).  Note: fdisk(8) and some early versions of DOS create
       all  partitions  with  the number of sectors already maxi-
       mized.  For more information,  see  the  maximize  command
       below.   The partition type can be one of Primary or Logi-
       cal.  For unallocated space on the  drive,  the  partition
       type  can also be Pri/Log, or empty (if the space is unus-
       able).  The filesystem type section displays the  name  of
       the  filesystem used on the partition, if known.  If it is
       unknown, then Unknown and the hex value of the  filesystem
       type  are displayed.  A special case occurs when there are
       sections of the disk drive that cannot  be  used  (because
       all  of  the  primary  partitions are used).  When this is
       detected, the filesystem type is  displayed  as  Unusable.
       The  size  field  displays  the  size  of the partition in
       megabytes (by default).  It can also display the  size  in
       sectors  and  cylinders  (see  the  change  units  command
       below).  If an asterisks (*) appears after the size,  this
       means that the partition is not aligned on cylinder bound-
       aries.

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 informa-
       tion in the partition table.  DOS FORMAT expects DOS FDISK
       to clear the first 512 bytes of the data area of a  parti-
       tion  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 cfdisk or fdisk to
       change the size of a DOS partition table entry,  then  you
       must  also use dd to zero the first 512 bytes of that par-
       tition before using DOS FORMAT to  format  the  partition.
       For example, if you were using cfdisk to make a DOS parti-
       tion table entry for /dev/hda1, then (after exiting  fdisk
       or  cfdisk 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. Note:

       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 fdisk or Linux cfdisk program.

COMMANDS
       cfdisk commands can be entered by pressing the desired key
       (pressing Enter after the command is not necessary).  Here
       is a list of the available commands:

       b      Toggle  bootable  flag  of  the  current partition.
              This allows you to select which  primary  partition
              is bootable on the drive.

       d      Delete  the  current  partition.  This will convert
              the current partition into free space and merge  it
              with  any  free  space  immediately surrounding the
              current partition.  A partition already  marked  as
              free space or marked as unusable cannot be deleted.

       g      Change the disk geometry (cylinders, heads, or sec-
              tors-per-track).   WARNING: This option should only
              be used by people who know what they are doing.   A
              command line option is also available to change the
              disk geometry.  While at the change  disk  geometry
              command  line,  you  can choose to change cylinders
              (c), heads (h), and sectors  per  track  (s).   The
              default  value  will be printed at the prompt which
              you can accept by simply pressing the Enter key, or
              you  can  exit  without changes by pressing the ESC
              key.  If you want to change the default value, sim-
              ply  enter  the desired value and press Enter.  The
              altered disk parameter values do  not  take  effect
              until  you  return the main menu (by pressing Enter
              or ESC at the change disk  geometry  command  line.
              If  you  change  the  geometry  such  that the disk
              appears larger, the extra sectors are added at  the
              end of the disk as free space.  If the disk appears
              smaller, the partitions that  are  beyond  the  new
              last  sector  are deleted and the last partition on
              the drive (or the free space  at  the  end  of  the
              drive) is made to end at the new last sector.

       h      Print the help screen.

       m      Maximize disk usage of the current partition.  This
              command will recover the the unused  space  between
              the partition table and the beginning of the parti-
              tion, but at  the  cost  of  making  the  partition
              incompatible  with  DOS,  OS/2  and  possibly other
              operating systems.  This option will toggle between
              maximal  disk  usage and DOS, OS/2, etc. compatible
              disk usage.  The default when creating a  partition
              is to create DOS, OS/2, etc. compatible partitions.

       n      Create new partition from free space.  If the  par-
              tition  type  is Primary or Logical, a partition of
              that type will be created,  but  if  the  partition
              type  is Pri/Log, you will be prompted for the type
              you want to create.  Be aware that  (1)  there  are
              only  four  slots  available for primary partitions
              and (2) since there can be only one extended parti-
              tion, which contains all of the logical drives, all
              of the logical drives must be contiguous  (with  no
              intervening   primary   partition).    cfdisk  next
              prompts you for the size of the partition you  want
              to  create.   The default size, equal to the entire
              free space of the current partition, is display  in
              megabytes.   You  can either press the Enter key to
              accept the default size or enter a  different  size
              at  the  prompt.   cfdisk  accepts  size entries in
              megabytes (M) [default], kilobytes  (K),  cylinders
              (C)  and sectors (S) by entering the number immedi-
              ately followed by one of (M, K, C or  S).   If  the
              partition  fills the free space available, the par-
              tition is created and you are returned to the  main
              command line.  Otherwise, the partition can be cre-
              ated at the beginning or the end of the free space,
              and  cfdisk  will  ask you to choose where to place
              the partition.  After  the  partition  is  created,
              cfdisk  automatically adjusts the other partition's
              partition types if all of  the  primary  partitions
              are used.

       p      Print  the  partition  table  to the screen or to a
              file. There are several different formats  for  the
              partition that you can choose from:

              r      Raw data format (exactly what would be writ-
                     ten to disk)

              s      Partition table in sector order format

              t      Partition table in raw format

              The raw data format will  print  the  sectors  that
              would  be  written  to  disk  if a write command is
              selected.  First, the primary  partition  table  is
              printed,  followed  by the partition tables associ-
              ated with each  logical  partition.   The  data  is
              printed in hex byte by byte with 16 bytes per line.

              The partition table in  sector  order  format  will
              print the partition table ordered by sector number.
              The fields, from left to right, are the  number  of
              the  partition,  the partition type, the first sec-
              tor, the last sector, the  offset  from  the  first
              sector  of  the partition to the start of the data,
              the length of the partition,  the  filesystem  type
              (with  the hex value in parenthesis), and the flags
              (with the hex value in parenthesis).   In  addition
              to  the  primary  and  logical partitions, free and
              unusable space is printed and the  extended  parti-
              tion is printed before the first logical partition.

              If a partition does not start or end on a  cylinder
              boundary  or if the partition length is not divisi-
              ble by the  cylinder  size,  an  asterisks  (*)  is
              printed  after the non-aligned sector number/count.
              This usually indicates that a partition was created
              by  an  operating system that either does not align
              partitions to cylinder boundaries or that used dif-
              ferent  disk geometry information.  If you know the
              disk geometry of the other  operating  system,  you
              could  enter  the  geometry  information  with  the
              change geometry command (g).

              For the first partition on the  disk  and  for  all
              logical  partitions,  if the offset from the begin-
              ning of the partition is not equal to the number of
              sectors per track (i.e., the data does not start on
              the first head), a number sign (#) is printed after
              the  offset.   For the remaining partitions, if the
              offset is not zero, a number sign will  be  printed
              after  the offset.  This corresponds to the NC flag
              in the partitions section of the main display.

              The partition table in raw format  will  print  the
              partition  table  ordered  by partition number.  It
              will leave out all free and  unusable  space.   The
              fields,  from  left to right, are the number of the
              partition, the flags (in hex), the  starting  head,
              sector  and  cylinder,  the filesystem ID (in hex),
              the ending head, sector and cylinder, the  starting
              sector  in  the partition and the number of sectors
              in the partition.  The information  in  this  table
              can  be directly translated to the raw data format.

              The partition  table  entries  only  have  10  bits
              available  to  represent  the  starting  and ending
              cylinders.  Thus, when the absolute starting  (end-
              ing)  sector  number  is on a cylinder greater than
              1023, the  maximal  values  for  starting  (ending)
              head, sector and cylinder are printed.  This is the
              method used by OS/2, and thus  fixes  the  problems
              associated  with  OS/2's fdisk rewriting the parti-
              tion table when it is not in  this  format.   Since
              Linux and OS/2 use absolute sector counts, the val-
              ues in the starting and  ending  head,  sector  and
              cylinder are not used.

       q      Quit  program.   This will exit the program without
              writing any data to disk.

       t      Change the filesystem type.  By default, new parti-
              tions  are  created  as Linux partitions, but since
              cfdisk can create partitions  for  other  operating
              systems,  change partition type allows you to enter
              the hex value of the filesystem you desire.  A list
              of the know filesystem types is displayed.  You can
              type in the filesystem type at the prompt or accept
              the default filesystem type [Linux].

       u      Change  units  of  the  partition size display.  It
              will rotate through megabytes, sectors  and  cylin-
              ders.

       W      Write  partition table to disk (must enter an upper
              case W).  Since this  might  destroy  data  on  the
              disk,  you must either confirm or deny the write by
              entering `yes' or `no'.  If you enter `yes', cfdisk
              will write the partition table to disk and the tell
              the kernel to re-read the partition table from  the
              disk.   The re-reading of the partition table works
              is most cases, but I  have  seen  it  fail.   Don't
              panic.   It  will  be  correct after you reboot the
              system.  In all cases, I still recommend  rebooting
              the system--just to be safe.

       Up Arrow

       Down Arrow
              Move  cursor to the previous or next partition.  If
              there are more partitions than can be displayed  on
              a  screen,  you can display the next (previous) set
              of partitions by  moving  down  (up)  at  the  last
              (first) partition displayed on the screen.

       CTRL-L Redraws  the  screen.  In case something goes wrong
              and you cannot read anything, you can  refresh  the
              screen from the main command line.

       ?      Print the help screen.

       All  of  the  commands can be entered with either upper or
       lower case letters (except for Writes).  When  in  a  sub-
       menu  or  at a prompt to enter a filename, you can hit the
       ESC key to return to the main command line.

OPTIONS
       -a     Use an arrow cursor instead of  reverse  video  for
              highlighting the current partition.

       -v     Print the version number and copyright.

       -z     Start  with zeroed partition table.  This option is
              useful when you want  to  repartition  your  entire
              disk.   Note:  this option does not zero the parti-
              tion table on the disk; rather,  it  simply  starts
              the  program without reading the existing partition
              table.

       -c cylinders

       -h heads

       -s sectors-per-track
              Override the number of cylinders, heads and sectors
              per  track  read  from  the  BIOS.  If your BIOS or
              adapter does not supply this information or  if  it
              supplies  incorrect  information, use these options
              to set the disk geometry values.

       -P opt Prints the partition table  in  specified  formats.
              opt can be one or more of "r", "s" or "t".  See the
              print command (above) for more information  on  the
              print formats.

EXIT STATUS
       0: No errors; 1: Invocation error; 2: I/O error; 3: cannot
       get geometry; 4: bad partition table on disk.

SEE ALSO
       fdisk(8)

BUGS
       The current version does not support multiple disks.

AUTHOR
       Kevin E. Martin (martin@cs.unc.edu)

The BOGUS Linux Release    3 June 1995                          1