How to format a disk or partition in Linux

Formatting a disk or partition in Linux writes a new filesystem layout to the target device so the kernel can mount it cleanly for application data, removable media, or a newly attached data volume.

Linux exposes storage as block devices such as /dev/vdb and /dev/vdb1. lsblk is the quickest way to identify the correct target and see whether it is already mounted, wipefs shows any filesystem signatures that are about to be replaced, mkfs.ext4 writes the new ext4 metadata, and blkid reads the new label, type, and UUID directly from the device after the format finishes.

Formatting is destructive because the old filesystem metadata is replaced immediately. The flow below uses ext4 on a current Ubuntu-based system and assumes the target is not the running root or boot filesystem; if the device still serves live workloads, unmount it first or continue from maintenance media instead. In minimal rescue or container environments, blkid is the more direct post-format confirmation because it reads the device itself instead of waiting for udev metadata to catch up.

1. List the available block devices to identify the exact disk or partition that should be formatted.

   $ lsblk -o NAME,SIZE,TYPE,FSTYPE,MOUNTPOINTS
   NAME          SIZE TYPE FSTYPE MOUNTPOINTS
   nvme0n1       100G disk
   |-nvme0n1p1   512M part vfat   /boot/efi
   `-nvme0n1p2  99.5G part ext4   /
   vdb            64G disk
   `-vdb1         64G part

   Use a partition path such as /dev/vdb1 when only one volume should be reformatted. Use a whole-disk path such as /dev/vdb only when the filesystem should live directly on the disk without partitions.

2. If the target from the previous step is mounted, unmount it before writing the new filesystem.

   $ sudo umount /dev/vdb1

   No output usually means the unmount completed cleanly.

   Related: How to unmount a disk in Linux

3. Inspect any existing signatures on the target before overwriting them.

   $ sudo wipefs --output DEVICE,OFFSET,TYPE,UUID,LABEL /dev/vdb1
   DEVICE OFFSET TYPE UUID      LABEL
   vdb1   0x36   vfat D408-739B USB
   vdb1   0x0    vfat D408-739B USB
   vdb1   0x1fe  vfat D408-739B USB

   If wipefs returns no data rows, the target does not currently expose a filesystem or partition-table signature that wipefs can identify.

4. Create the new ext4 filesystem and assign a label while writing the metadata.

   $ sudo mkfs.ext4 -L data /dev/vdb1
   Creating filesystem with 16384 4k blocks and 16384 inodes
   
   Allocating group tables: done
   Writing inode tables: done
   Creating journal (1024 blocks): done
   Writing superblocks and filesystem accounting information: done

   This step overwrites the previous filesystem metadata on the selected target. Replace data with the label required for that filesystem, and switch to another mkfs.* helper only when a different filesystem is intentionally required on the same confirmed device path.

5. Read the new filesystem metadata directly from the device to confirm that the format completed.

   $ sudo blkid /dev/vdb1
   /dev/vdb1: LABEL="data" UUID="0cb29b3d-16ed-499c-9ed3-4deca785119f" BLOCK_SIZE="4096" TYPE="ext4"

   This is the decisive success check for the format step. The UUID value is the stable identifier normally used later in /etc/fstab for persistent mounts.