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What is a Filesystem Table (fstab) in Linux and Why is It Important?

Posted on the 16 January 2023 by Top10

The filesystem table (fstab) is a system configuration file that is stored in the /etc directory on Linux and contains information about the various filesystems and how the system should mount them at boot time.

The Linux kernel uses the information in the fstab file to determine which filesystems to mount and where to mount them. Here's everything you need to know about fstab and Linux filesystems.

What is a file system?

A file system is the way a computer organizes and stores data on storage devices such as solid-state drives (SSDs) and flash drives.

Without file systems, it would be difficult to find and access certain files on a storage device, and the operating system would be unable to keep track of which areas of storage are in use and which are free.

In Linux, filesystems are very important for the following reasons:

  • Organization: They provide a directory hierarchy for better organization
  • Space Management: Your file system keeps track of used and free space on your storage device and allocates space for new files.
  • Security: Protect the integrity of files stored on a storage device, such as by using checksums or logging.

In addition, file systems provide support for file-level permissions, compression, or encryption.

Some common file systems include NTFS, FAT, ext4, etc. ext4 (Extended File System Version 4) is used on Linux and Unix systems.

Viewing and Understanding fstab in Linux

You can view the fstab file with Linux text editors such as nano or Vim, or with the cat command to display the output to the terminal.

The following example uses the Vim text editor:

vim /etc/fstab

The result of the command should be similar to the following:

The file contains a number of lines. Each line is separated by spaces and contains the following six sections:

1. File System (file system)

It contains the device or file system that the system should mount on boot. The mount command also uses fstab to mount the hard drive or any storage devices whenever you run the appropriate mount commands.

2. Mount Point (mount point)

The mount point specifies the directory where the storage device is to be mounted. The system needs to mount each file system to the correct directory.

For example, the root filesystem is usually mounted on the root directory (/) and is separate from user directories, which are mounted on the /home directory.

3. Type (type)

It defines the type of file system to use; some common ones include ext4, XFS, NTFS, etc.

The Linux kernel needs to know which driver to use to correctly access your file system, since different file systems have different capabilities and functions.

If the storage device has the wrong type value, you may experience file system errors.

4.Options

A comma-separated list of mount options for the specified storage device. Options control how your system mounts and uses file systems.

  • Auto: Automatically mount the file system at boot time.
  • Noauto: Do ​​not automatically mount the file system at boot time.
  • User: Allow any user to mount the file system.
  • Nouser: Allow only a privileged user to mount the filesystem.
  • Sync: Use synchronous I/O for the file system.

Some common options include:

5. Dump

This flag specifies whether the dump utility should back up the file system. The default value is 0, which means no backup.

You can set the dump flag to 1 or 2 for the file systems you want to include in the backup.

6. Fsck

This flag specifies the order in which fsck (filesystem check) should check filesystems on boot. The fsck utility on Linux systems checks and restores the integrity of a file system. The default value is 0, which means do not check the file system.

  • 1. Check the file system first.
  • 2. Check the file system after checking all file systems with the fsck flag set to 1.
  • 3. Check the file system after checking all file systems with fsck flag 1 or 2.

Other possible values:

If you want to check your filesystems every time, set the value to more than 2.

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