fstab

Warning: These examples may crash your computer if there is something incorrect. For example, setting the wrong UUID in /etc/fstab will make the system crash or unbootable. Ensure you put the correct values in the /etc/fstab file. The author is not responsible for any damage. It is also recommended to always create a backup of the fstab file before any editing.

The /etc/fstab (file system table) file is a critical configuration file in Linux that tells the system how to mount partitions and storage devices automatically during boot.

It consists of six fields, separated by tabs or spaces.

The 6 Fields of /etc/fstab

Field Name Description Example

1 Device The identifier for the partition (UUID, Label, or /dev path). UUID=123-abc

2 Mount Point The directory where the filesystem will be attached. /home

3 FS Type The type of filesystem (ext4, xfs, vfat, ntfs-3g, swap). ext4

4 Options Specific mount settings (comma-separated, no spaces). defaults,ro

5 Dump Used by the dump utility (0 = skip, 1 = backup). 0

6 FSCK The order in which fsck checks the disk (0=none, 1=root, 2=others). 2

Detailed Breakdown

1. Device (The "What")

While you can use /dev/sda1, modern systems prefer UUID (Universally Unique Identifier) or LABEL. This ensures that even if you move the hard drive to a different SATA port, the system still finds the correct partition.

2. Mount Point (The "Where")

This is the directory where the files will appear.

• Note: For swap partitions, this field is simply written as none or swap.

3. Filesystem Type

You must specify the correct driver. Common types include:

• ext4: Standard Linux filesystem.

• xfs: High-performance 64-bit journaling filesystem.

• vfat: Used for EFI partitions or USB sticks.

• nfs: For network-attached storage.

4. Mount Options

The defaults option typically includes rw, suid, dev, exec, auto, nouser, and async. Other important flags:

• noauto: The partition is not mounted at boot (only when you manually run mount).

• user: Allows a non-root user to mount the drive.

• ro: Mounts the filesystem as Read-Only.

5. Dump (The "Backup")

This is rarely used today. It’s almost always 0 (do not back up).

6. FSCK (The "Check")

This determines the priority for the filesystem check at boot:

• 1: Reserved for the root (/) partition.

• 2: For all other partitions.

• 0: Do not check (used for swap or network drives).

Tips

If you modify /etc/fstab and want to test it without rebooting, run the command:

mount -a

When editing the file with vi, you may want to insert the output from a command into a file, immediately after the cursor:

:r!command

You can use this to insert the UUID of a disk so you don't have to copy that long string. You can execute something like this:

:r!sudo blkid | grep sr0

Then you can edit the line and remove the unwanted parts.