fdisk – Easy Way To Manage Disk Partitions In Linux

Hard disks can be divided into one or more logical disks called partitions.

This division is described in the partition table (MBR or GPT) found in sector 0 of the disk.

Linux needs at least one partition, namely for its root file system and we can’t install Linux OS without partitions.

Once created, a partition must be formatted with an appropriate file system before files can be written to it.

To do so, we need some utility to perform this in Linux.

There are many utilities are available for that in Linux. We had written about Parted Command in the past and today we are going to discuss about fdisk.

fdisk command is one of the the best tool to manage disk partitions in Linux.

It supports maximum 2 TB, and everyone prefer to go with fdisk.

This tool is used by vast of Linux admin because we don’t use more than 2TB now a days due to LVM and SAN. It’s used in most of the infra structure around the world.

Still if you want to create a large partitions, like more than 2TB then you have to go either Parted Command or cfdisk Command.

Disk partition and file system creations is one of the routine task for Linux admin.

If you are working on vast environment then you have to perform this task multiple times in a day.

How Linux Kernel Understand Hard Disks?

As a human we can easily understand things but computer needs the proper naming conversion to understand each and everything.

In Linux, devices are located on /dev partition and Kernel understand the hard disk in the following format.

  • /dev/hdX[a-z]: IDE Disk is named hdX in Linux
  • /dev/sdX[a-z]: SCSI Disk is named sdX in Linux
  • /dev/xdX[a-z]: XT Disk is named sdX in Linux
  • /dev/vdX[a-z]: Virtual Hard Disk is named vdX in Linux
  • /dev/fdN: Floppy Drive is named fdN in Linux
  • /dev/scdN or /dev/srN: CD-ROM is named /dev/scdN or /dev/srN in Linux

What Is fdisk Command?

fdisk stands for fixed disk or format disk is a cli utility that allow users to perform following actions on disks. It allows us to view, create, resize, delete, move and copy the partitions.

It understands MBR, Sun, SGI and BSD partition tables and it doesn’t understand GUID Partition Table (GPT) and it is not designed for large partitions.

fdisk allows us to create a maximum of four primary partitions per disk. One of these may be an extended partition and it holds multiple logical partitions.

1-4 is reserved for four primary partitions and Logical partitions start numbering from 5.

How To Install fdisk On Linux

You don’t need to install fdisk in Linux system because it has installed by default as part of core utility.

How To List Available Disks Using fdisk Command

First we have to know what are the disks were added in the system before performing any action. To list all available disks on your system run the following command.

It lists possible information about the disks such as disk name, how many partitions are created in it, Disk Size, Disklabel type, Disk Identifier, Partition ID and Partition Type.

$ sudo fdisk -l
Disk /dev/sda: 30 GiB, 32212254720 bytes, 62914560 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
Disklabel type: dos
Disk identifier: 0xeab59449

Device     Boot    Start      End  Sectors Size Id Type
/dev/sda1  *    20973568 62914559 41940992  20G 83 Linux


Disk /dev/sdb: 10 GiB, 10737418240 bytes, 20971520 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 /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 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 /dev/sdd: 10 GiB, 10737418240 bytes, 20971520 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 /dev/sde: 10 GiB, 10737418240 bytes, 20971520 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

How To List A Specific Disk Partitions Using fdisk Command

If you would like to see a specific disk and it’s partitions, use the following format.

$ sudo fdisk -l /dev/sda
Disk /dev/sda: 30 GiB, 32212254720 bytes, 62914560 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
Disklabel type: dos
Disk identifier: 0xeab59449

Device     Boot    Start      End  Sectors Size Id Type
/dev/sda1  *    20973568 62914559 41940992  20G 83 Linux

How To List Available Actions For fdisk Command

When you hit m in the fdisk command that will show you available actions for fdisk command.

$ sudo fdisk /dev/sdc

Welcome to fdisk (util-linux 2.30.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0xe944b373.

Command (m for help): m

Help:

  DOS (MBR)
   a   toggle a bootable flag
   b   edit nested BSD disklabel
   c   toggle the dos compatibility flag

  Generic
   d   delete a partition
   F   list free unpartitioned space
   l   list known partition types
   n   add a new partition
   p   print the partition table
   t   change a partition type
   v   verify the partition table
   i   print information about a partition

  Misc
   m   print this menu
   u   change display/entry units
   x   extra functionality (experts only)

  Script
   I   load disk layout from sfdisk script file
   O   dump disk layout to sfdisk script file

  Save & Exit
   w   write table to disk and exit
   q   quit without saving changes

  Create a new label
   g   create a new empty GPT partition table
   G   create a new empty SGI (IRIX) partition table
   o   create a new empty DOS partition table
   s   create a new empty Sun partition table

How To List Partitions Types Using fdisk Command

When you hit l in the fdisk command that will show you an available partitions type for fdisk command.

$ sudo fdisk /dev/sdc

Welcome to fdisk (util-linux 2.30.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0x9ffd00db.

Command (m for help): l

 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 or  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 ea  Rufus alignment
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a5  FreeBSD         eb  BeOS fs        
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a6  OpenBSD         ee  GPT            
10  OPUS            55  EZ-Drive        a7  NeXTSTEP        ef  EFI (FAT-12/16/
11  Hidden FAT12    56  Golden Bow      a8  Darwin UFS      f0  Linux/PA-RISC b
12  Compaq diagnost 5c  Priam Edisk     a9  NetBSD          f1  SpeedStor      
14  Hidden FAT16 <3 61  SpeedStor       ab  Darwin boot     f4  SpeedStor      
16  Hidden FAT16    63  GNU HURD or Sys af  HFS / HFS+      f2  DOS secondary  
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fb  VMware VMFS    
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fc  VMware VMKCORE 
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid fd  Linux raid auto
1c  Hidden W95 FAT3 75  PC/IX           bc  Acronis FAT32 L fe  LANstep        
1e  Hidden W95 FAT1 80  Old Minix       be  Solaris boot    ff  BBT            

How To Create A Disk Partition Using fdisk Command

If you would like to create a new partition use the following steps. In my case, i'm going to create 4 partitions (3 Primary and 1 Extended) on /dev/sdc disk. To the same for other partitions too.

As this takes value from partition table so, hit Enter for first sector. Enter the size which you want to set for the partition (We can add a partition size using KB,MB,G and TB) for last sector.

For example, if you would like to add 1GB partition then the last sector value should be +1G. Once you have created 3 partitions, it will automatically change the partition type to extended as a default. If you still want to create a fourth primary partitions then hit p instead of default value e.

$ sudo fdisk /dev/sdc

Welcome to fdisk (util-linux 2.30.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): Enter

Using default response p.
Partition number (1-4, default 1): Enter
First sector (2048-20971519, default 2048): Enter
Last sector, +sectors or +size{K,M,G,T,P} (2048-20971519, default 20971519): +1G

Created a new partition 1 of type 'Linux' and of size 1 GiB.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 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
Disklabel type: dos
Disk identifier: 0x8cc8f9e5

Device     Boot Start     End Sectors Size Id Type
/dev/sdc1        2048 2099199 2097152   1G 83 Linux

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

How To Create A Extended Disk Partition Using fdisk Command

Make a note, you have to use remaining all space when you create a extended partition because again you can able to create multiple logical partition in that.

$ sudo fdisk /dev/sdc

Welcome to fdisk (util-linux 2.30.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n
Partition type
   p   primary (3 primary, 0 extended, 1 free)
   e   extended (container for logical partitions)
Select (default e): Enter

Using default response e.
Selected partition 4
First sector (6293504-20971519, default 6293504): Enter
Last sector, +sectors or +size{K,M,G,T,P} (6293504-20971519, default 20971519): Enter

Created a new partition 4 of type 'Extended' and of size 7 GiB.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 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
Disklabel type: dos
Disk identifier: 0x8cc8f9e5

Device     Boot   Start      End  Sectors Size Id Type
/dev/sdc1          2048  2099199  2097152   1G 83 Linux
/dev/sdc2       2099200  4196351  2097152   1G 83 Linux
/dev/sdc3       4196352  6293503  2097152   1G 83 Linux
/dev/sdc4       6293504 20971519 14678016   7G  5 Extended

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

How To View Unpartitioned Disk Space Using fdisk Command

As described in the above section, we have totally created 4 partitions (3 Primary and 1 Extended). Extended partition disk space will show unpartitioned until you create a logical partitions in that.

Use the following command to view the unpartitioned space for a disk. As per the below output we have 7GB unpartitioned disk.

$ sudo fdisk /dev/sdc

Welcome to fdisk (util-linux 2.30.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): F
Unpartitioned space /dev/sdc: 7 GiB, 7515144192 bytes, 14678016 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

  Start      End  Sectors Size
6293504 20971519 14678016   7G

Command (m for help): q

How To Create A Logical Partition Using fdisk Command

Follow the same above procedure to create a logical partition once you have created the extended partition.
Here, i have created 1GB of logical partition called /dev/sdc5, you can double confirm this by checking the partition table value.

$ sudo fdisk /dev/sdc

Welcome to fdisk (util-linux 2.30.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): n
All primary partitions are in use.
Adding logical partition 5
First sector (6295552-20971519, default 6295552): Enter
Last sector, +sectors or +size{K,M,G,T,P} (6295552-20971519, default 20971519): +1G

Created a new partition 5 of type 'Linux' and of size 1 GiB.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 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
Disklabel type: dos
Disk identifier: 0x8cc8f9e5

Device     Boot   Start      End  Sectors Size Id Type
/dev/sdc1          2048  2099199  2097152   1G 83 Linux
/dev/sdc2       2099200  4196351  2097152   1G 83 Linux
/dev/sdc3       4196352  6293503  2097152   1G 83 Linux
/dev/sdc4       6293504 20971519 14678016   7G  5 Extended
/dev/sdc5       6295552  8392703  2097152   1G 83 Linux

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

How To Delete A Partition Using fdisk Command

If the partition is no more used in the system than we can remove it by using the below steps.

Make sure you have to enter the correct partition number to delete it. In this case, i'm going to remove /dev/sdc2 partition.

$ sudo fdisk /dev/sdc

Welcome to fdisk (util-linux 2.30.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): d
Partition number (1-5, default 5): 2

Partition 2 has been deleted.

Command (m for help): p
Disk /dev/sdc: 10 GiB, 10737418240 bytes, 20971520 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
Disklabel type: dos
Disk identifier: 0x8cc8f9e5

Device     Boot   Start      End  Sectors Size Id Type
/dev/sdc1          2048  2099199  2097152   1G 83 Linux
/dev/sdc3       4196352  6293503  2097152   1G 83 Linux
/dev/sdc4       6293504 20971519 14678016   7G  5 Extended
/dev/sdc5       6295552  8392703  2097152   1G 83 Linux

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

How To Format A Partition Or Create A FileSystem On The Partition

In computing, a file system or filesystem controls how data is stored and retrieved through inode tables.

Without a file system, the system can't find where the information is stored on the partition. Filesystem can be created in three ways. Here, i'm going to create a filesystem on /dev/sdc1 partition.

$ sudo mkfs.ext4 /dev/sdc1
or
$ sudo mkfs -t ext4 /dev/sdc1
or
$ sudo mke2fs /dev/sdc1

mke2fs 1.43.5 (04-Aug-2017)
Creating filesystem with 262144 4k blocks and 65536 inodes
Filesystem UUID: c0a99b51-2b61-4f6a-b960-eb60915faab0
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

When you creating a filesystem on tha partition that will create the following important things on it.

  • Filesystem UUID: UUID stands for Universally Unique Identifier, UUIDs are used to identify block devices in Linux. It's 128 bit long numbers represented by 32 hexadecimal digits.
  • Superblock: Superblock stores metadata of the file system. If the superblock of a file system is corrupted, then the filesystem cannot be mounted and thus files cannot be accessed.
  • Inode: An inode is a data structure on a filesystem on a Unix-like operating system that stores all the information about a file except its name and its actual data.
  • Journal: A journaling filesystem is a filesystem that maintains a special file called a journal that is used to repair any inconsistencies that occur as the result of an improper shutdown of a computer.

How To Mount A Partition In Linux

Once you have created the partition and filesystem then we need to mount the partition to use.

To do so, we need to create a mountpoint to mount the partition. Use mkdir command to create a mountpoint.

$ sudo mkdir -p /mnt/2g-new

For temporary mount, use the following command. You will be lose this mountpoint after rebooting your system.

$ sudo mount /dev/sdc1 /mnt/2g-new

For permanent mount, add the partition details in the fstab file. It can be done in two ways either adding device name or UUID value.

Permanent mount using Device Name:

# vi /etc/fstab

/dev/sdc1 /mnt/2g-new ext4 defaults 0 0

Permanent mount using UUID Value. To get a UUID of the partition use blkid command.

$ sudo blkid
/dev/sdc1: UUID="d17e3c31-e2c9-4f11-809c-94a549bc43b7" TYPE="ext2" PARTUUID="8cc8f9e5-01"
/dev/sda1: UUID="d92fa769-e00f-4fd7-b6ed-ecf7224af7fa" TYPE="ext4" PARTUUID="eab59449-01"
/dev/sdc3: UUID="ca307aa4-0866-49b1-8184-004025789e63" TYPE="ext4" PARTUUID="8cc8f9e5-03"
/dev/sdc5: PARTUUID="8cc8f9e5-05"
# vi /etc/fstab

UUID=d17e3c31-e2c9-4f11-809c-94a549bc43b7 /mnt/2g-new ext4 defaults 0 0

The same has been verified using df Command.

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            969M     0  969M   0% /dev
tmpfs           200M  7.0M  193M   4% /run
/dev/sda1        20G   16G  3.0G  85% /
tmpfs           997M     0  997M   0% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           997M     0  997M   0% /sys/fs/cgroup
tmpfs           200M   28K  200M   1% /run/user/121
tmpfs           200M   25M  176M  13% /run/user/1000
/dev/sdc1      1008M  1.3M  956M   1% /mnt/2g-new

Magesh Maruthamuthu

Love to play with all Linux distribution

You may also like...

Shares
Close
Please support the site
By clicking any of these buttons you help our site to get better