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Linux 2.6 - man page for cfdisk (linux section 8)

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

       cfdisk - Curses/slang based disk partition table manipulator for Linux

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

       cfdisk is a curses/slang based program for partitioning any hard disk drive.  Typical val-
       ues of the device argument are:

	      /dev/hda [default]

       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 geometry used by cfdisk is found as
       follows. First the partition table is examined, to see what geometry was used by the  pre-
       vious  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 geometry 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  parti-
       tions, the command line and a warning line.  The header contains the program name and ver-
       sion 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 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 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 sectors 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

       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 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 com-
       mand "dd if=/dev/zero of=/dev/hda1 bs=512 count=1" to zero the first 512 bytes of the par-
       tition. 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 exam-
       ple,  you  should make DOS partitions with the DOS FDISK program and Linux partitions with
       the Linux fdisk or Linux cfdisk program.

       cfdisk commands can be entered by pressing the desired key (pressing Enter after the  com-
       mand 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 parti-
	      tion.  A partition already marked as free space or marked  as  unusable  cannot  be

       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  sec-
	      tors  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  press-
	      ing 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 operat-
	      ing  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],  kilo-
	      bytes  (K),  cylinders  (C) and sectors (S) by entering the number immediately fol-
	      lowed 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 partition 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 usually indicates that a partition was  cre-
	      ated  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 num-
	      ber 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 parti-
	      tion 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 cylin-
	      der,  the  starting sector in the partition and the number of sectors in the parti-
	      tion.  The information in this table can be directly translated  to  the	raw  data

	      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 parti-
	      tions, 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, sec-
	      tors 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-read-
	      ing of the partition table does not work in some cases, for example for device-map-
	      per  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.

       -a     Use  an  arrow  cursor instead of reverse video for highlighting the current parti-

       -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 reparti-
	      tion 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

       -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 incor-
	      rect 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 for-

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

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

       The current version does not support multiple disks.

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

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

The BOGUS Linux Release 		   3 June 1995					CFDISK(8)

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