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



NAME
       cfdisk - Curses based disk partition table manipulator for Linux

SYNOPSIS
       cfdisk [-agvz] [-c cylinders] [-h heads] [-s sectors-per-track] [-P opt] [device]

DESCRIPTION
       cfdisk  is  a curses based program for partitioning any hard disk drive.  Typical values of the device argument
       are:

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

       Note that cfdisk does not align partitions to block device  I/O  limits.  This  functionality  is  provided  by
       fdisk(8).

       In  order  to write the partition table cfdisk needs something called the 'geometry' of the disk: the number of
       'heads' and the number of 'sectors per track'. Linux does not use any geometry, so if  the  disk  will  not  be
       accessed by other operating systems, you can safely accept the defaults that cfdisk chooses for you. The geome-
       try used by cfdisk is found as follows. First the partition table is examined, to see what geometry was used by
       the  previous  program that changed it. If the partition table is empty, or contains garbage, or does not point
       at a consistent geometry, the kernel is asked for advice. If nothing works 255 heads and  63  sectors/track  is
       assumed.  The geometry can be overridden on the command line or by use of the 'g' command. When partitioning an
       empty large modern disk, picking 255 heads and 63 sectors/track is always a good idea.  There is no need to set
       the number of cylinders, since cfdisk knows the disk size.

       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 displayed and the program will exit.  This might also be caused by incorrect geom-
       etry  information,  and  can be overridden on the command line.  Another way around this problem 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
       geometry.  The partitions section always displays the current partition table.  The command line is  the  place
       where  commands  and  text are entered.  The available commands are usually displayed in brackets.  The warning
       line is usually 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 partition.

       The format of the partition table in the partitions section 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 desig-
       nates 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" sec-
       tors with the maximize command (m).  Note: fdisk(8) and some early versions of DOS create all  partitions  with
       the  number of sectors already maximized.  For more information, see the maximize command below.  The partition
       type can be one of Primary or Logical.  For unallocated space on the drive, the  partition  type  can  also  be
       Pri/Log,  or empty (if the space is unusable).  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 sec-
       tors and cylinders (see the change units command below).  If an asterisk (*) appears after the size, this means
       that the partition is not aligned on cylinder boundaries.

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 FOR-
       MAT 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 partition before using DOS FORMAT to format the partition.
       For  example,  if  you were using cfdisk to make a DOS partition 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 use-
       less.

       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 sectors-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, simply enter the desired value and press Enter.  The  altered  disk  parameter
              values do not take effect until you return to 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 unused space between the
              partition table and the beginning of the partition, 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 partition 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 partition, 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 displayed 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 immediately followed by one of (M, K, C or S).
              If the partition fills the free space available, the partition is created and you are  returned  to  the
              main  command  line.   Otherwise,  the  partition can be created 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 partitions' 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 parti-
              tion that you can choose from:


              r      Raw data format (exactly what would be written 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  associated  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  sector,  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 partition 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  divisible
              by  the  cylinder size, an asterisk (*) is printed after the non-aligned sector number/count.  This usu-
              ally indicates that a partition was created by an operating system that either does not align partitions
              to  cylinder boundaries or that used different 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 beginning 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 (ending) 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 partition table when it is not in
              this  format.   Since  Linux  and OS/2 use absolute sector counts, the values 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 partitions 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 cylinders.

       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 does not  work  in  some  cases,  for  example  for  device-mapper
              devices.   In  particular case you need to inform kernel about new partitions by partprobe(8), kpartx(8)
              or reboot the system.

       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.

       -g     Do not use the geometry given by the disk driver, but try to guess a geometry from the partition  table.

       -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 partition 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), sfdisk(8), mkfs(8), parted(8), partprobe(8), kpartx(8)

BUGS
       The current version does not support multiple disks.

AUTHOR
       Kevin E. Martin (martinATcs.edu)


AVAILABILITY
       The  cfdisk  command  is  part  of  the  util-linux-ng   package   and   is   available   from   ftp://ftp.ker-
       nel.org/pub/linux/utils/util-linux-ng/.



The BOGUS Linux Release           3 June 1995                        CFDISK(8)