use of fstab option for mounting disk in linux

Use of fstab option for Mounting Disk in Linux Permanent

Mounting Disk in Linux using fstab Option

What is Mounting Disk in Linux

Mounting disk in Linux is actually a process to access a partitioned and formatted hard disk in the system. Whatever data is stored in a hard disk can only be accessed or used after mounting that hard disk in Linux Operating System. As we know when a pen drive is inserted in the USB slot of Windows system, the pen drive will automatically be available for access in the windows home folder. This is only due to “plug and play” options installed in Windows operating system. But, in Linux, inserting or connecting a hard disk in the system, is not enough to access that disk. Before accessing it, the hard disk has to partitioned, formatted followed by mounting it in the system. However, the hard disk can be mounted with any of the single or multiple folder of Linux system. There is no restriction of mounting location of that hard disk. The following diagram is explained the basic difference between inserting a hard disk in Linux and Windows operating system.

use of fstab option for mounting disk in linux - Difference between Mounting Disk in Linux and Windows
Difference between Mounting Disk in Linux and Windows

Requirement before Mounting Disk in Linux

A new hard disk can not be used with Linux system directly. Before using it, the following have to be ensured :-

  • Partitioning of the hard disk with use of “fdisk” command
  • Formatting the hard disk with use of command “mkfs“. Formatting is basically process of configuring the file system of the disk. There are many kinds of file system for Linux system is available :-
    • cramfs
    • ext2
    • ext3
    • ext4
    • fat
    • minix
    • msdos
    • vfat
    • xfs
    • swap

To understand the procedure of partitioning and formatting of a hard disk, you can follow the blog “Fdisk command to create and delete partition in Linux“.

Use of fstab Option

What is fstab Option

Mounting a disk in any folder is being done by command “mount“, but such mounting is not permanent in nature. The mounted disk will automatically be unmounted after shutting down the system. When the system will reboot, the mounted disk will be disappeared. The disk must again be mounted for use or access. To avoid such process of mounting a disk again and again with every system boot, we have to mount the disk permanently. To make stable the mounting, fstab option should be used with some statement entry in “fstab” file is required. This “fstab” file is kept in /etc directory by default. Full form of “fstab” can be elaborated to understand as “File System Table”. In this file, a table of instructions for each permanently mounted hard disk is being maintained. If we read the file “fstab“, a table will be shown with some entry. The following diagram will be explained the line of instructions of this file :-

use of fstab option for mounting disk in linux - File System Table (fstab) Entry Explained
File System Table (fstab) Entry Explained

There will be six columns in the table of “fstab” file. Each column require specific entry related to the mounted disk.

First Column of fstab Option

The disk device will be denoted in this column with its name-id with absolute path or UUID (universal Unique ID). The default location of each and every hard disk will be “/dev

Name-id of a all the Hard Disk of a System

fdisk -l

use of fstab option for mounting disk in linux - Command to Know the Name-id and Particulars of All the Hard Disks
Command to Know the Name-id and Particulars of All the Hard Disks

Description : The name-id including its all particulars like absolute path, size, sectors, partitioning profile etc of each hard disk will be displayed. The hard disk will be displayed as sda, sdb, sdc … and so on. Generally, sda will be the system hard disk in which Linux OS is installed. On adding a new hard disk in the system, the same will be named as “sdb“. Accordingly, adding of more hard disk will be shown as “sdc“, “sdb“… etc.

Name-id of a Particular Hard Disk of a System

fdisk -l /dev/sdc

use-of-fstab-option-for-mounting-disk-in-linux-Command-to-Know-the-Name-id-and-Particulars-of-a-Specific-Hard-Disk-2
Command-to-Know-the-Name-id-and-Particulars-of-a-Specific-Hard-Disk-2

Description : Particulars of hard disk “sdc” will be displayed with its all available partitioned profile. The partitioned portion of the hard disk will be named serially as “sdc1“, “sdc2“, “sdc3” and onward in a table. In Cent_OS 8, the size of partitioned portion will also be displayed before ID column of the table.

Name-id of a Particular Hard Disk of a System in Short

fdisk -l | grep /dev/sdc

use of fstab option for mounting disk in linux - Command to Know the Name-id and Particulars of a Specific Hard Disk in Short
Command to Know the Name-id and Particulars of a Specific Hard Disk in Short

Description : Very short particulars of the hard disk will be displayed. Even table heading will not be shown.

View Size of Hard Disk with its Partition

lsblk

use of fstab option for mounting disk in linux - Command to View Disk Tree with Size of its Partition
Command to View Disk Tree with Size of its Partition

Description : A table of all the available hard disk tree with its partitions including name-id and size will be displayed.

UUID and File System of a Hard Disk

blkid

use of fstab option for mounting disk in linux - Command to Know the UUID and File System of Hard Disk
Command to Know the UUID and File System of Hard Disk

Description : UUID of all the hard disk with its name-id including File system information will be displayed.

Second Column of fstab Option

This column is specified to denote the location of the mounted disk with absolute path. As we know, hard disk can be mounted any of the folder or sub folder of the system, the location with absolute path must be mentioned here during editing of “fstab” file. For mounting a hard disk in a system in multiple folders, the entry should be made separately for each folder. If the hard disk has mounted in “c1data” of “zivi” folder under “home” directory, then the path should be mentioned as “/home/zivi/c1data“.

Third Column of fstab Option

This column is specified to denote file system of disk. File system, which has configured during formatting of the disk, can be seen with use of command “blkid“, already explained above under heading “UUID and File System of a Hard Disk”

Fourth Column of fstab Option

This column is specified to denote various mount option including permissions etc. Generally, this is set as “default” by the system for normal user or normal use of disk. The mount option may be changed according to user requirement when a specific disk to be mounted for a specific type of job. Multiple mount options can also be used separated by commas.

Fifth Column of fstab Option

This column is specified to denote willingness to get dump backup of the partition. The value zero (0) denotes “no backup” and the value one (1) denotes “dump backup” of the partition. However, this column may be left blank if, no backup option is required.

Sixth Column of fstab Option

This column is specified to denote file system check priority for fs checks regarding errors of partition at the time of system boot. File system check at the time system boot is good idea to keep disk update all time, but this process will be time consuming. It will take much time to ready a system for use after booting. Therefore, generally, the fs checks order set to zero (0) for no checking. However, priority for checking of disk can be set in order of numerical numbers such as 1, 2, 3 ….. onward.

Mounting Disk in Linux

Mounting a Hard Disk Partition in Linux

mount /dev/sdc1 /home/zivi/c1data

use of fstab option for mounting disk in linux - Command for Mounting a Disk
Command for Mounting a Disk

Description : On listing of folder c1data under /home/zivi/, no file or folder found. After mounting the partition sdc1 in the folder c1data under /home/zivi/, a folder “profile” found in the folder “c1data“. Hence, the folder “profile” kept in hard disk “sdc1“. After re-boot the disk sdc1 will automatically be unmounted.

Mounting a CD ROM in Linux

mount /dev/cdrom /mnt/mycd

Description : A cdrom device mounted in “mycd” folder of “mnt” directory.

Mounting an ISO image in Linux

mount -o loop centos8.iso /mnt/cos8

Description : the iso image file “centols8.iso” mounted in the folder “cos8” in the directory “mnt”

Unmounting disk

umount /home/zivi/c1data

use of fstab option for mounting disk in linux - Command for Unmounting a Disk
Command for Un-mounting a Disk

Description : After un-mounting the disk from “c1data” folder, the folder “profile” removed.

Mounting a Hard Disk Permanently in Linux

Mount a Hard Disk in Linux

Firstly, create a mounting mount in the folder “mnt” as “hdc1“. Then, use following command to mount the disk “sdc1” into the folder “hdc1” of “mnt” folder.

mount /dev/sdc1 /mnt/hdc1

use of fstab option for mounting disk in linux - Creating a Mounting Point and Mounting a Disk
Creating a Mounting Point and Mounting a Disk

Description : The disk sdc1 mounted in the folder “hdc1” of “mnt” directory temporarily.

Use of fstab Option

Read fstab file kept in /etc Directory

cat /etc/fstab

use of fstab option for mounting disk in linux - Reading fstab File
Reading fstab File

Description : Check the list of disk and device already entered in the file “fstab” and ensure the value of new device is not already entered in the table of “fstab” file.

Edit fstab file Kept in /etc Directory with vi Editor

vi /etc/fstab

use of fstab option for mounting disk in linux - Open fstab File for Editing in VI editor
Open fstab File for Editing in VI editor

Press “I” to insert/edit value in the file “fstab“. Make entry in last row of the table regarding value of “sdc1” disk as under

/dev/sdc1 /mnt/hdc1 ext4 default 0 0

In the above row, you can enter UUID of the disk in place of name id i.e., “/dev/sdc1“. You can find UUID of the disk by using command “blkid“.

use of fstab option for mounting disk in linux - Press I button to Edit the fstab File
Press I button to Edit and Make Entry of New Disk in Last Row

Press “Esc” button to quit edit option and entering command option. Then just press ” :wq” to save and quite the “vi” editor.

use of fstab option for mounting disk in linux - Saving and Closing the VI Editor after Editing
Saving and Closing the VI Editor after Editing

Press Enter button to quit from “vi” editor.

use of fstab option for mounting disk in linux - Closing VI Editor and Return to Linux Cursor
Closing VI Editor and Return to Linux Cursor

Now the entry of “sdc1” disk has been made in the file “fstab” in /etc and the said disk has permanently mounted in the system. After re-booting, the disk will not unmounted automatically as usual.

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