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    The following form allows you to view linux man pages.

    Command:

    fdisk

    
    
    

    SYNOPSIS

           fdisk [-uc] [-b sectorsize] [-C cyls] [-H heads] [-S sects] device
    
           fdisk -l [-u] [device...]
    
           fdisk -s partition...
    
           fdisk -v
    
           fdisk -h
    
    
    

    DESCRIPTION

           Hard  disks can be divided into one or more logical disks called parti-
           tions.  This division is described in the partition table found in sec-
           tor 0 of the disk.
    
           In the BSD world one talks about 'disk slices' and a 'disklabel'.
    
           Linux  needs  at  least one partition, namely for its root file system.
           It can use swap files and/or swap partitions, but the latter  are  more
           efficient. So, usually one will want a second Linux partition dedicated
           as swap partition.  On Intel compatible hardware, the BIOS  that  boots
           the  system can often only access the first 1024 cylinders of the disk.
           For this reason people with large disks often create a third partition,
           just  a  few  MB large, typically mounted on /boot, to store the kernel
           image and a few auxiliary files needed at boot time, so as to make sure
           that  this  stuff  is  accessible to the BIOS.  There may be reasons of
           security, ease of administration and backup, or testing,  to  use  more
           than the minimum number of partitions.
    
           fdisk  (in  the  first form of invocation) is a menu driven program for
           creation and manipulation of partition tables.  It understands DOS type
           partition tables and BSD or SUN type disklabels.
    
           fdisk  doesn't  understand  GUID  Partition  Table  (GPT) and it is not
           designed for large partitions. In particular case use more advanced GNU
           parted(8).
    
           The device is usually /dev/sda, /dev/sdb or so. A device name refers to
           the entire disk.  The old systems without libata (a library used inside
           the  Linux  kernel  to support ATA host controllers and devices) make a
           difference between IDE and SCSI disks. In such a case the  device  name
           will be /dev/hd* (IDE) or /dev/sd* (SCSI).
    
           The  partition  is  a  device name followed by a partition number.  For
           example, /dev/sda1 is the first partition on the first hard disk in the
           system.    See   also   Linux   kernel  documentation  (the  Documenta-
           tion/devices.txt file).
    
           A BSD/SUN type disklabel can describe 8 partitions, the third of  which
           should  be  a  'whole  disk'  partition.  Do not start a partition that
           actually uses its first sector (like a swap partition) at  cylinder  0,
           tions.  In  sector  0 there is room for the description of 4 partitions
           (called 'primary'). One of these may be an extended partition; this  is
           a  box  holding  logical partitions, with descriptors found in a linked
           list of sectors, each preceding the corresponding  logical  partitions.
           The  four primary partitions, present or not, get numbers 1-4.  Logical
           partitions start numbering from 5.
    
           In a DOS type partition table the starting offset and the size of  each
           partition  is  stored  in  two  ways:  as an absolute number of sectors
           (given in 32 bits) and as a Cylinders/Heads/Sectors  triple  (given  in
           10+8+6  bits).  The former is OK - with 512-byte sectors this will work
           up to 2 TB. The latter has two different problems. First of all,  these
           C/H/S fields can be filled only when the number of heads and the number
           of sectors per track are known. Secondly, even if we  know  what  these
           numbers  should be, the 24 bits that are available do not suffice.  DOS
           uses C/H/S only, Windows uses both, Linux never uses C/H/S.
    
           If possible, fdisk will obtain the disk geometry  automatically.   This
           is  not necessarily the physical disk geometry (indeed, modern disks do
           not really have anything like a physical geometry, certainly not  some-
           thing  that  can  be  described  in  simplistic Cylinders/Heads/Sectors
           form), but is the disk geometry that MS-DOS uses for the partition  ta-
           ble.
    
           Usually all goes well by default, and there are no problems if Linux is
           the only system on the disk. However, if the disk has to be shared with
           other  operating  systems, it is often a good idea to let an fdisk from
           another operating system make at least one partition. When Linux  boots
           it looks at the partition table, and tries to deduce what (fake) geome-
           try is required for good cooperation with other systems.
    
           Whenever a partition table is printed out, a consistency check is  per-
           formed  on  the  partition table entries.  This check verifies that the
           physical and logical start and end points are identical, and  that  the
           partition  starts and ends on a cylinder boundary (except for the first
           partition).
    
           Some versions of MS-DOS create a first partition which does  not  begin
           on  a cylinder boundary, but on sector 2 of the first cylinder.  Parti-
           tions beginning in cylinder 1 cannot begin on a cylinder boundary,  but
           this  is  unlikely  to  cause  difficulty  unless you have OS/2 on your
           machine.
    
           A sync() and a BLKRRPART ioctl() (reread partition table from disk) are
           performed  before  exiting  when  the partition table has been updated.
           Long ago it used to be necessary to reboot after the use of  fdisk.   I
           do  not  think this is the case anymore - indeed, rebooting too quickly
           might cause loss of not-yet-written data. Note that both the kernel and
           the disk hardware may buffer data.
    
    
    

    DOS 6.x WARNING

           would  use the command "dd if=/dev/zero of=/dev/sda1 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 fdisk or Linux cfdisk
           program.
    
    
    

    OPTIONS

           -b sectorsize
                  Specify the sector size of the disk. Valid values are 512, 1024,
                  2048  or  4096.   (Recent kernels know the sector size. Use this
                  only on old kernels or to override the  kernel's  ideas.)  Since
                  util-linux-ng  2.17  fdisk  differentiates  between  logical and
                  physical sector size. This option changes both sector  sizes  to
                  sectorsize.
    
           -h     Print help and then exit.
    
           -c     Switch off DOS-compatible mode. (Recommended)
    
           -C cyls
                  Specify the number of cylinders of the disk.  I have no idea why
                  anybody would want to do so.
    
           -H heads
                  Specify the number of heads of the disk. (Not the physical  num-
                  ber, of course, but the number used for partition tables.)  Rea-
                  sonable values are 255 and 16.
    
           -S sects
                  Specify the number of sectors per track of the disk.   (Not  the
                  physical  number,  of  course, but the number used for partition
                  tables.)  A reasonable value is 63.
    
           -l     List the partition tables for the  specified  devices  and  then
                  exit.   If no devices are given, those mentioned in /proc/parti-
                  tions (if that exists) are used.
    
           -u     When listing partition tables, give sizes in sectors instead  of
                  cylinders.
    
           -s partition
                  The size of the partition (in blocks) is printed on the standard
                  output.
    
           -v     Print version number of fdisk program and exit.
    
           parted  does  much  more:  it not only resizes partitions, but also the
           filesystems that live in them.
    
           The IRIX/SGI type disklabel is currently not supported by  the  kernel.
           Moreover, IRIX/SGI header directories are not fully supported yet.
    
           The option 'dump partition table to file' is missing.
    
    
    

    SEE ALSO

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

    AVAILABILITY

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

    Linux 2.0 11 June 1998 FDISK(8)

    
    
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