fdisk command examples

Linux fdisk - Manipulating the Partition Table

fdisk Command


The fdisk command is used to display or manipulate your partition tables on your Linux system. "fdisk" is a menu driven utility that is used to work with physical disks.

The basic syntax of the fdisk command is: fdisk [device]

fdisk accepts single keystrokes followed by pressing the "Enter" key. fdisk can also be used to quickly display your partition table outside of the interactive menu system.




root@john-desktop:~# fdisk -l

Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders, total 312581808 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000132a7 Device Boot Start End Blocks Id System /dev/sda1 * 2048 307357695 153677824 83 Linux /dev/sda2 307359742 312580095 2610177 5 Extended /dev/sda5 307359744 312580095 2610176 82 Linux swap / Solaris

To enter the interactive menu you have to issue: fdisk device

! ! WARNING: fdisk can delete partitions which can cause data loss and make your system not bootable ! !
! ! You should only use fdisk if you fully understand what you are doing.

fdisk Interactive Help Menu



root@john-desktop:~# fdisk /dev/sda

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the DOS compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help):

To access the above menu, I issued the command "fdisk /dev/sda". I then keyed in "m" for the help menu. Any commands that I use from this menu will work only with the device "/dev/sda". It is imperative you are sure that you have the correct device! When working with Primary and Extended partitions the choice number of 1 to 4 is offered. Logical partitions are only available when an Extended partition has been created. Logical partition numbers are from 5 to 16.


Commonly used options


a
Toggles the boot partition "on" or "off"

d
Delete a partition. You will be asked to specify the partition number that you require deleting.

l
List known partition types:



 0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris        
 1  FAT12           27  Hidden NTFS Win 82  Linux swap / So c1  DRDOS/sec (FAT-
 2  XENIX root      39  Plan 9          83  Linux           c4  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     85  Linux extended  c7  Syrinx         
 5  Extended        41  PPC PReP Boot   86  NTFS volume set da  Non-FS data    
 6  FAT16           42  SFS             87  NTFS volume set db  CP/M / CTOS / .
 7  HPFS/NTFS/exFAT 4d  QNX4.x          88  Linux plaintext de  Dell Utility   
 8  AIX             4e  QNX4.x 2nd part 8e  Linux LVM       df  BootIt         
 9  AIX bootable    4f  QNX4.x 3rd part 93  Amoeba          e1  DOS access     
 a  OS/2 Boot Manag 50  OnTrack DM      94  Amoeba BBT      e3  DOS R/O        
 b  W95 FAT32       51  OnTrack DM6 Aux 9f  BSD/OS          e4  SpeedStor      
 c  W95 FAT32 (LBA) 52  CP/M            a0  IBM Thinkpad hi eb  BeOS fs        
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a5  FreeBSD         ee  GPT            
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a6  OpenBSD         ef  EFI (FAT-12/16/
10  OPUS            55  EZ-Drive        a7  NeXTSTEP        f0  Linux/PA-RISC b
11  Hidden FAT12    56  Golden Bow      a8  Darwin UFS      f1  SpeedStor      
12  Compaq diagnost 5c  Priam Edisk     a9  NetBSD          f4  SpeedStor      
14  Hidden FAT16 <3 61  SpeedStor       ab  Darwin boot     f2  DOS secondary  
16  Hidden FAT16    63  GNU HURD or Sys af  HFS / HFS+      fb  VMware VMFS    
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE 
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fd  Linux RAID auto
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid fe  LANstep        
1c  Hidden W95 FAT3 75  PC/IX           be  Solaris boot    ff  BBT            
1e  Hidden W95 FAT1 80  Old Minix 


m
Interactive Help Menu.

n
New partition, Here you will be prompted for partition type - "Primary", "Extended" or "Logical"
See example of "n" option in use: Example of fdisk in use

p
Display Partition table. The partition information displayed is currently stored in memory. Any changes made are only reflected when they have been written using the "w" option.

q
Quit fdisk without making any changes.

t
Change partition System ID (type). This are the numbers that are displayed when using the "l" option.

w
Write any changes made to disk. Changes are only made when this option has been selected.


partprobe command


When you have made changes to your systems partition table. You may be required to force your system to re-read its partition table. This is often preferable to re-booting your system.

The basic syntax of the Linux partprobe command is: partprobe [-d] [-s] [devices....]

Partprobe Options

-d
Don't update the kernel.

-s
Display a summary of devices and their partitions.

-h
Show summary of options.

Output from partprobe command

root@john-desktop:~# partprobe -s
/dev/sda: msdos partitions 1 2 <5>