Control Mounting and Unmounting of Filesystems Part 2

In this guide, you’ll learn how to grant non-root users the ability to mount and unmount filesystems on Linux. While root or sudo privileges have traditionally been required, desktop environments and modern distributions often auto-mount removable media such as CD-ROMs, USB flash drives, and external disks under a user’s home directory:

/media/USER/LABEL

For example, if john plugs in a USB drive labeled FlashDrive, it appears at:

/media/john/FlashDrive

Allowing Non-Root Mounts via /etc/fstab

You can configure /etc/fstab to let normal users mount and unmount specific devices without sudo. Modify the mount options field to include one of the following:

Example: permitting all users to mount /dev/sdb1 on /mnt/userdrive:

/dev/sdb1  /mnt/userdrive  ext4  defaults,user  0 0

mount /mnt/userdrive
umount /mnt/userdrive

Managing Mounts with systemd

systemd can manage both static mounts and on-demand automounts via unit files in /etc/systemd/system/. Units must be named after the mount point by replacing slashes with hyphens and appending .mount or .automount.

Creating a Mount Unit

1. Create the file /etc/systemd/system/mnt-external.mount:

   sudo vi /etc/systemd/system/mnt-external.mount
   

2. Populate it:

   [Unit]
   Description=External data disk
   
   [Mount]
   What=/dev/disk/by-uuid/56C11DCC5D2E1334
   Where=/mnt/external
   Type=ntfs
   Options=defaults
   
   [Install]
   WantedBy=multi-user.target
   

3. Reload systemd and start the mount:

   sudo systemctl daemon-reload
   sudo systemctl start mnt-external.mount
   

4. Check status:

   sudo systemctl status mnt-external.mount
   

   Sample output:

   ● mnt-external.mount — External data disk
        Loaded: loaded (/etc/systemd/system/mnt-external.mount; disabled; preset: enabled)
        Active: active (mounted) since Mon 2019-08-19 22:27:02 -03; 14s ago
         What: /dev/sdb1
         Where: /mnt/external
   

5. To auto-mount at boot:

   sudo systemctl enable mnt-external.mount
   

Creating an Automount Unit

An automount unit triggers the mount only when the directory is accessed. You’ll need both the .mount and a corresponding .automount file.

1. Create /etc/systemd/system/mnt-external.automount:

   sudo vi /etc/systemd/system/mnt-external.automount
   

2. Add:

   [Unit]
   Description=Automount External Data Disk
   
   [Automount]
   Where=/mnt/external
   
   [Install]
   WantedBy=multi-user.target
   

3. Reload, start, and enable:

   sudo systemctl daemon-reload
   sudo systemctl start mnt-external.automount
   sudo systemctl enable mnt-external.automount
   

Now, whenever you ls /mnt/external, systemd will mount the disk automatically.

Links and References

• fstab(5) Manual
• systemd.mount Documentation
• systemd.automount Documentation