The /etc/fstab file on Linux Explained

To use a hard disk partition or external file system, we need to mount it on the Linux file system. There are two ways to mount a disk partition or external file system: temporary and permanent. We use the mount command to mount it temporarily and the /etc/fstab file to mount it permanently.

The /etc/fstab file stores mount points' information. The kernel reads this file at the boot time to mount partitions to the Linux file system. If we want to mount a partition permanently, we must create an entry for that partition in this file.

A fstab file entry has six fields. The following table explains their meanings.

Using the /etc/fstab

Let us take an example to understand how to use the /etc/fstab file to mount partitions permanently.

Suppose you attached a new hard disk to the system and created partitions. You can use the fdisk -l command to list partitions on a disk. The following image shows a new hard disk with partitions.

Now suppose, you want to mount these partitions permanently. To mount a partition permanently, you need to create an entry in the /etc/fstab file. The kernel reads and uses this file at the boot time to mount partitions.

Before we create entries for our partitions, let us take the backup of the current file. A backup copy allows us to restore the system to a working state if we make any mistakes.

To mount a partition, we need a directory. To mount four partitions, we need four directories. Create four directories.

Open the /etc/fstab file and create entries for the partitions at the end of existing entries.

In the first field, specify the absolute path of the partition you want to mount.

In the second field, specify the directory on which you want to mount the partition specified in the first field.

In the third field, you need to specify the partition's file system.

The fourth field describes the mount options associated with the filesystem. For practice, you can use the default option here.

In the fifth and sixth fields, use a value of zero.

The dump command uses the fifth field to determine whether the mounted device or partition needs to be dumped during the boot time.

The fsck command uses the sixth field to determine whether it should check the file system on the mounted partition or device.

To enable these options, we need to use a value of one in these fields. If we enable these options, it will improve system performance and increase the boot time. You can turn these options on or off on a production system based on your requirements. Since we created these partitions only for practice, we do not need to enable these options.

Save the file.

To test these partitions, restart the system.

The kernel reads the /etc/fstab file to mount partitions at boot time. If it fails to mount any partition, it halts the boot process. If the system boots normally, it verifies all partitions specified in the fstab file have been mounted successfully.

After restart, we can use the lsblk command to list partitions.

As we can see in the above output, all partitions are mounted successfully. It verifies the /etc/fstab file entries.

Conclusion

The /etc/fstab file saves information about partitions. The boot process reads this file to mount partitions on the file system. It is a regular text file. You can edit or update this file based on your requirements.