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fdisk Command in Linux
NAME
fdisk - Partition table manipulator for Linux
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 partitions. This division is described in the partition table found in sector 0 of the disk.OPTIONS
| TAG | DESCRIPTION |
|---|---|
| -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 number, of course, but the number used for partition tables.) Reasonable 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/partitions (if that exists) are used |
EXAMPLES
EXAMPLE-1:
To list all existing disk partition on your system.
# fdisk -l
output:
# fdisk -l
Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders, total 41943040 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: 0x000dd3ab
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 499711 248832 83 Linux
/dev/sda2 501758 41940991 20719617 5 Extended
/dev/sda5 501760 41940991 20719616 8e Linux LVM
Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders, total 41943040 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: 0x00000000
Disk /dev/sdb doesn't contain a valid partition table
Disk /dev/mapper/ubuntu--vg-root: 20.1 GB, 20124270592 bytes
255 heads, 63 sectors/track, 2446 cylinders, total 39305216 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: 0x00000000
Disk /dev/mapper/ubuntu--vg-root doesn't contain a valid partition table
Disk /dev/mapper/ubuntu--vg-swap_1: 1069 MB, 1069547520 bytes
255 heads, 63 sectors/track, 130 cylinders, total 2088960 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: 0x00000000
Disk /dev/mapper/ubuntu--vg-swap_1 doesn't contain a valid partition table
EXAMPLE-2:
To view all partitions of specific hard disk use the option ‘-l‘ with device name.
# fdisk -l /dev/sda
output:
Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders, total 41943040 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: 0x000dd3ab
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 499711 248832 83 Linux
/dev/sda2 501758 41940991 20719617 5 Extended
/dev/sda5 501760 41940991 20719616 8e Linux LVM
EXAMPLE-3:
To view all commands which are available for fdisk.
# fdisk /dev/sda
Type ‘m‘ to see the list of all available commands of fdisk which can be operated on /dev/sda hard disk:
output:
# fdisk /dev/sda
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x18b2eab2.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
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
EXAMPLE-4:
To print all partition table of hard disk, you must be on command mode of specific hard disk say /dev/sda.:
# fdisk /dev/sda
From the command mode, enter ‘p‘ instead of ‘m‘ as we did earlier. As I enter ‘p‘, it will print the specific /dev/sda partition table.
output:
Command (m for help): p Disk /dev/sda: 637.8 GB, 637802643456 bytes 255 heads, 63 sectors/track, 77541 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 13 104391 83 Linux /dev/sda2 14 2624 20972857+ 83 Linux /dev/sda3 2625 4582 15727635 83 Linux /dev/sda4 4583 77541 586043167+ 5 Extended /dev/sda5 4583 5887 10482381 83 Linux /dev/sda6 5888 7192 10482381 83 Linux
EXAMPLE-5:
enter ‘d‘ to delete any given partition name from the system:
# fdisk /dev/sda
output:
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x18b2eab2.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): d Partition number (1-4): 4 Command (m for help): w
EXAMPLE-6:
After entering in command mode, now press “n” command to create a new partition under /dev/sda with specific size. This can be demonstrated with the help of following given output.:
# fdisk /dev/sda
output:
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x18b2eab2.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): n Command action e extended p primary partition (1-4) e
After the new partition is created, don’t skip to format the newly created partition using ‘mkfs‘ command. Type the following command in the terminal to format a partition. Here /dev/sda4 is my newly created partition.:
# mkfs.ext4 /dev/sda4
EXAMPLE-7:
To check the size of that partition using flag ‘s‘ (displays size in blocks) with fdisk command. This way you can check size of any specific device.:
# fdisk -s /dev/sda2
output:
5194304
EXAMPLE-8:
To Fix Partition Table Order:
# fdisk /dev/sda
output:
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x18b2eab2.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): x Done.
EXAMPLE-9:
To Quit without saving changes.
# fdisk /dev/sda
output:
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x18b2eab2.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): q Done.
EXAMPLE-10:
To verify partition table# fdisk /dev/sda
output:
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x18b2eab2.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
Command (m for help): v
Remaining 41439231 unallocated 512-byte sectors
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