Mounting File Systems

Imagine you have a new hard drive, USB stick, or a network share. For your Linux server to use it, you need to mount its file system.

Mounting is like telling your server: "Hey, this storage device contains files, and I want to access them through this specific directory." Until mounted, the storage device is just raw hardware.

The primary command to attach a file system to your server's directory tree is mount. It connects a specific device (like a partition) to a designated directory, called a mount point.

The basic syntax is:

• mount [device] [mount_point]

You'll often need sudo for this command as it involves system-level changes.

Let's say you have a new partition at /dev/sdb1 and you want to access its contents in a folder called /mnt/new_drive. First, ensure the mount point directory exists!

Try running this example. It simulates mounting and then listing its content.

A mount point is simply an empty directory on your existing file system where the contents of another file system will become accessible.

• Common mount points are in /mnt (for temporary mounts) or /media (for removable media).
• You must create the mount point directory before you can mount anything to it.
• If the directory isn't empty, its existing contents will be hidden until the file system is unmounted.

Just as you mount a file system, you must also unmount it before physically disconnecting the device or if you no longer need it. This ensures all pending write operations are completed and data isn't corrupted.

The command for this is umount (note: no 'n' after 'u'!). You can unmount by specifying either the device or the mount point.

• umount [device]
• umount [mount_point]

If you try to unmount a file system that is currently in use (e.g., a user has opened a file or is in that directory), you'll get a "device is busy" error. You might need to close applications or navigate out of the directory.

Let's unmount our previous example. After unmounting, the mount point directory will appear empty again.

Manually mounting devices is fine for temporary use, but what if you want a file system to be mounted automatically every time your server boots up?

That's where the /etc/fstab file comes in. It's a system configuration file that lists all the disks and partitions that should be mounted automatically at boot time, and how they should be mounted.

Each line in /etc/fstab represents a file system to be mounted and has six fields, separated by spaces or tabs:

• 1. Device: The partition or device to mount (e.g., /dev/sdb1 or UUID=...).
• 2. Mount Point: The directory where the device will be mounted (e.g., /data).
• 3. File System Type: The type of file system (e.g., ext4, xfs, ntfs).
• 4. Options: Mount options (e.g., defaults, noauto, ro).
• 5. Dump: Used by the dump utility (0 to disable).
• 6. Pass: Controls file system check order at boot (0 to disable, 1 for root, 2 for others).

Using UUIDs (Universally Unique Identifiers) instead of device names (like /dev/sdb1) is highly recommended in /etc/fstab. UUIDs are unique and persistent, unlike device names which can change after a reboot or adding new hardware.

Here's an example entry for a data partition:

Which of the following statements about mounting file systems in Linux are TRUE?

In this lesson, you learned the essentials of mounting file systems on Linux. We covered:

• Using the mount command to make storage devices accessible.
• The importance of mount points and how to create them.
• Safely detaching file systems with the umount command.
• Configuring automatic, persistent mounts using the /etc/fstab file.
• Understanding the structure and fields of an /etc/fstab entry, including the use of UUIDs.

Mastering these concepts is crucial for managing storage on your Linux server!