How to format disks and partitions in Linux

Formatting disks and partitions in Linux prepares storage for reliable data use, removes obsolete filesystem structures, and aligns space usage with new workloads. Correct formatting is especially important when reusing drives from other systems or converting removable media for use with Linux tools. Choosing an appropriate filesystem also affects performance, maximum file sizes, and compatibility with other operating systems.

Under Linux, the family of mkfs utilities creates filesystems on block devices such as /dev/sda2 or /dev/sdb1. Each filesystem type has a dedicated helper, for example mkfs.ext4 for ext4, mkfs.btrfs for Btrfs, or mkfs.vfat for FAT32 and exFAT. The selected helper writes superblocks, allocation tables, journals, and other on-disk structures that define how files and directories are stored.

Formatting always overwrites an existing filesystem and destroys the data stored on it. Confirming the correct device name before running any mkfs command avoids damaging the system disk or other important volumes. Unmounting the target partition and ensuring that no services depend on it reduces the risk of corruption and guarantees a clean filesystem layout.

Related: How to mount disks and partitions in Linux
Related: How to get disk and partition UUIDs in Linux
Related: How to check disk errors in Linux

Steps to format disk and partition in Linux:

  1. Open a terminal with sudo privileges.
  2. List available disks and partitions and note device names and sizes. 
    $ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0   512M  0 loop /mnt/bench
loop1    7:1    0   300M  0 loop /mnt/format-prep
nbd0    43:0    0     0B  0 disk 
nbd1    43:32   0     0B  0 disk 
nbd2    43:64   0     0B  0 disk 
nbd3    43:96   0     0B  0 disk 
nbd4    43:128  0     0B  0 disk 
nbd5    43:160  0     0B  0 disk 
nbd6    43:192  0     0B  0 disk 
nbd7    43:224  0     0B  0 disk 
vda    254:0    0   1.8T  0 disk 
`-vda1 254:1    0   1.8T  0 part /etc/hosts
                                 /etc/hostname
                                 /etc/resolv.conf
vdb    254:16   0 606.5M  1 disk 
nbd8    43:256  0     0B  0 disk 
nbd9    43:288  0     0B  0 disk 
nbd10   43:320  0     0B  0 disk 
nbd11   43:352  0     0B  0 disk 
nbd12   43:384  0     0B  0 disk 
nbd13   43:416  0     0B  0 disk 
nbd14   43:448  0     0B  0 disk 
nbd15   43:480  0     0B  0 disk

    The NAME column maps to device paths such as /dev/loop1, while SIZE and MOUNTPOINTS help identify the intended disk.

  3. Confirm the exact device intended for formatting using size and mountpoint information. 
    $ df -h /root
Filesystem      Size  Used Avail Use% Mounted on
overlay         1.8T   17G  1.7T   1% /

    Formatting the wrong device such as /dev/vda instead of a loop device permanently destroys the existing filesystem and its data.

  4. Unmount the target partition if a mountpoint is listed in lsblk or df output. 
    $ sudo umount /dev/loop1

    No output from umount indicates the partition is now detached.

  5. Verify that the target partition is no longer mounted. 
    $ lsblk /dev/loop1
NAME  MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop1   7:1    0  300M  0 loop
  6. List available filesystem-specific mkfs helpers on the system. 
    $ ls /sbin/mkfs.*
/sbin/mkfs.bfs
/sbin/mkfs.cramfs
/sbin/mkfs.ext2
/sbin/mkfs.ext3
/sbin/mkfs.ext4
/sbin/mkfs.minix

    Typing mkfs. and pressing <TAB> twice in many shells shows the same helpers via completion.

  7. Format the target partition with the desired filesystem type and optional label. 
    $ sudo mkfs.ext4 -F -L data /dev/loop1
mke2fs 1.47.0 (5-Feb-2023)
Discarding device blocks:     0/76800           done                            
Creating filesystem with 76800 4k blocks and 76800 inodes
Filesystem UUID: 71cbb0a9-ef27-4ce6-98e9-1f67d2fea5cf
Superblock backups stored on blocks: 
	32768

Allocating group tables: 0/3   done                            
Writing inode tables: 0/3   done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: 0/3   done

    Running mkfs.ext4 on an existing partition erases all contained files and directories and cannot be undone.

  8. Check the new filesystem type and UUID for the formatted partition. 
    $ sudo blkid /dev/loop1
/dev/loop1: LABEL="data" UUID="71cbb0a9-ef27-4ce6-98e9-1f67d2fea5cf" BLOCK_SIZE="4096" TYPE="ext4"

    The UUID value is suitable for use in /etc/fstab to configure persistent mounts.

  9. Create a temporary mountpoint directory for the new filesystem. 
    $ sudo mkdir -p /mnt/format-demo
  10. Mount the new filesystem on the temporary mountpoint. 
    $ sudo mount /dev/loop1 /mnt/format-demo

    For permanent configuration, define a dedicated mountpoint and a corresponding entry in /etc/fstab as described in How to mount disks and partitions in Linux.

  11. Verify that the mounted filesystem is accessible and initially empty. 
    $ ls -A /mnt/format-demo
lost+found
$ df -h /mnt/format-demo
Filesystem      Size  Used Avail Use% Mounted on
/dev/loop1      265M   24K  244M   1% /mnt/format-demo
  12. Unmount the filesystem again if the temporary mount is no longer required. 
    $ sudo umount /mnt/format-demo