Welcome to Linux Knowledge Base and Tutorial
"The place where you learn linux"
Connect for Kids

 Create an AccountHome | Submit News | Your Account  

Tutorial Menu
Linux Tutorial Home
Table of Contents

· Introduction to Operating Systems
· Linux Basics
· Working with the System
· Shells and Utilities
· Editing Files
· Basic Administration
· The Operating System
· The X Windowing System
· The Computer Itself
· Networking
· System Monitoring
· Solving Problems
· Security
· Installing and Upgrading
· Linux and Windows

Glossary
MoreInfo
Man Pages
Linux Topics
Test Your Knowledge

Site Menu
Site Map
FAQ
Copyright Info
Terms of Use
Privacy Info
Disclaimer
WorkBoard
Thanks
Donations
Advertising
Masthead / Impressum
Your Account

Communication
Feedback
Forums
Private Messages
Surveys

Features
HOWTOs
News Archive
Submit News
Topics
User Articles
Web Links

Google
Google


The Web
linux-tutorial.info

Who's Online
There are currently, 62 guest(s) and 0 member(s) that are online.

You are an Anonymous user. You can register for free by clicking here

  

cfdisk




SYNOPSIS

       cfdisk [ -agvz ] [ -c cylinders ] [ -h heads ] [  -s  sec­
       tors-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

       In order to write the partition table cfdisk  needs  some­
       thing  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 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 geome­
       try 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  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
       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.


       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
              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.
              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.


       -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), mkfs(8), parted(8), sfdisk(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                  CFDISK(8)
  
Help us cut cost by not downloading the whole site!
Use of automated download sofware ("harvesters") such as wget, httrack, etc. causes the site to quickly exceed its bandwidth limitation and therefore is expressedly prohibited. For more details on this, take a look here

Login
Nickname

Password

Security Code
Security Code
Type Security Code


Don't have an account yet? You can create one. As a registered user you have some advantages like theme manager, comments configuration and post comments with your name.

Help if you can!


Amazon Wish List

Did You Know?
The Linux Tutorial welcomes your suggestions and ideas.


Friends



Tell a Friend About Us

Bookmark and Share



Web site powered by PHP-Nuke

Is this information useful? At the very least you can help by spreading the word to your favorite newsgroups, mailing lists and forums.
All logos and trademarks in this site are property of their respective owner. The comments are property of their posters. Articles are the property of their respective owners. Unless otherwise stated in the body of the article, article content (C) 1994-2013 by James Mohr. All rights reserved. The stylized page/paper, as well as the terms "The Linux Tutorial", "The Linux Server Tutorial", "The Linux Knowledge Base and Tutorial" and "The place where you learn Linux" are service marks of James Mohr. All rights reserved.
The Linux Knowledge Base and Tutorial may contain links to sites on the Internet, which are owned and operated by third parties. The Linux Tutorial is not responsible for the content of any such third-party site. By viewing/utilizing this web site, you have agreed to our disclaimer, terms of use and privacy policy. Use of automated download software ("harvesters") such as wget, httrack, etc. causes the site to quickly exceed its bandwidth limitation and are therefore expressly prohibited. For more details on this, take a look here

PHP-Nuke Copyright © 2004 by Francisco Burzi. This is free software, and you may redistribute it under the GPL. PHP-Nuke comes with absolutely no warranty, for details, see the license.
Page Generation: 0.09 Seconds