Disk Management in Linux: A Complete Guide to Partitioning and Mounting

Introduction / Why This Is Needed

Disk management is one of the key tasks for a Linux system administrator. Without proper partitioning, formatting, and mounting, you won't be able to use new disks or redistribute space. This guide will walk you through all the basic steps: from viewing existing disks to setting up permanent mounting. After completing it, you'll be able to confidently work with block devices in Linux.

Requirements / Preparation

Before you begin, ensure that:

1. You have access to a Linux terminal (Ubuntu, Debian, CentOS, or another systemd-based distribution).
2. You have superuser (sudo) privileges to perform disk operations.
3. Basic utilities are installed: fdisk (usually in the util-linux package), lsblk, e2fsprogs (for ext4). They are present by default in most distributions.
4. Critically important: If the target disk contains important data, back it up. Partitioning operations are irreversible.

Step 1: Viewing Current Disks and Partitions

First, determine which disks and partitions already exist in the system. Use two main commands:

lsblk

This command outputs a tree of all block devices (disks, partitions) in a convenient format. Pay attention to the columns: NAME (device name, e.g., sda1), SIZE (size), MOUNTPOINT (mount point, if the partition is already mounted).

sudo fdisk -l

More detailed information. Shows partition tables for each disk, partition type, start/end. Requires sudo to read all devices.

Example lsblk output:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   100G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0  99.5G  0 part /
sdb      8:16   0   20G   0 disk 

Here we see two disks (sda and sdb). sdb has no partitions and is not mounted—a candidate for work.

Step 2: Creating a New Partition on the Disk

Let's say we want to create a single partition using the entire disk sdb. Use fdisk (interactive) or parted (more modern). For simplicity and broad support, we'll use fdisk.

sudo fdisk /dev/sdb

You'll enter interactive mode. Type the following commands (each on a separate line, confirming with Enter):

1. n — create a new partition.
2. p — partition type (primary).
3. 1 — partition number (first).
4. Press Enter twice to accept defaults (start and end of the disk).
5. w — write changes and exit.

⚠️ Important: If the disk already has partitions, fdisk may ask you to delete them first (d). Be careful—this will destroy data.

Check the result:

lsblk /dev/sdb

Now you should see sdb1.

Step 3: Formatting the Partition to a Filesystem

The created partition sdb1 is still empty—it needs to be formatted. The choice of filesystem depends on your needs:

• ext4 — the most common, reliable, suitable for most tasks.
• xfs — efficient for very large disks and files, often used on servers.
• btrfs — modern, with snapshot and compression support.

For a general case, use ext4:

sudo mkfs.ext4 /dev/sdb1

The process will take a few seconds. The mkfs command is a frontend for specific utilities (mkfs.ext4).

💡 Tip: To find the partition's UUID (a unique identifier that doesn't change upon reconnection), run sudo blkid after formatting. You'll need it for /etc/fstab.

Step 4: Mounting the Partition Manually

Now the partition is ready for use. Create a directory that will be the mount point:

sudo mkdir -p /mnt/mydata

Mount the partition:

sudo mount /dev/sdb1 /mnt/mydata

Check:

df -h

You should see /dev/sdb1 in the list with the mount point /mnt/mydata. The partition is available for read/write.

⚠️ Important: This is a temporary mount. After a reboot, the partition will not mount automatically. For permanent mounting, proceed to the next step.

Step 5: Setting Up Automatic Mounting via /etc/fstab

The /etc/fstab file (file systems table) contains information about all permanent filesystems. Add a line for our partition there.

Open the file in an editor (e.g., sudo nano /etc/fstab) and add this line at the end:

UUID=your-partition-uuid /mnt/mydata ext4 defaults 0 2

How to get the UUID? Run sudo blkid and copy the value for /dev/sdb1 (e.g., UUID="a1b2c3d4-...").

Field explanation:

1. UUID=... — the partition's unique identifier (more reliable than /dev/sdb1, since device names can change).
2. /mnt/mydata — the mount point (must exist).
3. ext4 — filesystem type.
4. defaults — standard options (rw,suid,dev,exec,auto,nouser,async).
5. 0 — do not dump (for dump, usually 0).
6. 2 — filesystem check order at boot (1 for root /, 2 for others).

Check fstab correctness without risk:

sudo mount -a

If there are no errors, the configuration is correct. The partition will mount automatically on every boot.

Verifying the Result

1. Ensure the partition is mounted: mount | grep mydata or df -h.
2. Try creating a file: sudo touch /mnt/mydata/test.txt.
3. Reboot the system (sudo reboot), and after booting, check that the partition is mounted again (df -h).

Possible Issues

• Error "mount: /mnt/mydata: special device /dev/sdb1 does not exist." — The partition was not created or an incorrect device name is specified. Check lsblk.
• Error "wrong fs type, bad option, bad superblock" — The filesystem does not match what's specified in fstab or the partition is not formatted. Ensure the type in fstab (ext4) matches the actual one (sudo blkid).
• Partition does not mount after boot — Check /etc/fstab syntax (spaces/tabs), existence of the mount point, and that the auto option is present in defaults.
• Access error when mounting without sudo — In fstab, for a partition that should be mountable by a regular user, add the user option instead of defaults (but this reduces security).