Why are there so many loop partitions in my Ubuntu Linux system?

If you’ve been dabbling around with the Linux operating system, especially Ubuntu, you might have noticed numerous loop partitions appearing in your system. Often ranging in small sizes such as a mere few megabytes, you might wonder why these partition systems exist, what purpose they serve, and if they can be deleted to reclaim disk space.

One quick glance at your disk information through the ‘fdisk -l’ command might reveal a handful of “/dev/loop” entries before the actual hard drive data gets displayed. Are these loop partition systems essential or can they be tinkered with? Before we answer this question, let’s delve into the nature of these loop devices.

In this tutorial you will learn:

  • What are Loop Devices
  • Why are Loop Devices Used
  • Inspecting Loop Devices in Ubuntu
Why are there so many loop partitions in my Ubuntu Linux system?
Why are there so many loop partitions in my Ubuntu Linux system?
Software Requirements and Linux Command Line Conventions
Category Requirements, Conventions or Software Version Used
System Any Linux distro
Software N/A
Other Privileged access to your Linux system as root or via the sudo command.
Conventions # – requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
$ – requires given linux commands to be executed as a regular non-privileged user

What are Loop Devices?

Loop devices or loop mounts are a unique feature in Linux systems. They enable binding a regular file to a special block device, thereby creating a virtual file system. This facilitates a bunch of files to be packed together for access by the operating system. Programs such as snaps, which require isolated system operation, find loop devices extremely useful.

Loop devices essentially allow you to mount regular files as file systems, giving the benefit of working in an isolated environment, increasing security, and allowing developers to package apps with all the dependencies in a single snap.

Ubuntu Loop Partitions
Ubuntu Loop Partitions

Why are Loop Devices Used?

Loop devices, while primarily simulating a virtual file system, serve several purposes:

  1. They can facilitate the installation of an operating system over a file system, eliminating the need for drive repartitioning.
  2. They provide a convenient method of configuring system images post-mounting.
  3. They offer substantial data segregation.
  4. They enable sandboxed applications to include all required dependencies.
  5. Advanced developers can leverage isolated file systems to uniquely enhance the capabilities of an application.

Overall, with loop devices, the possibilities can be limitless.

Understanding Snap and Loop Partitions in Ubuntu

The reason why Ubuntu users encounter so many loop partitions is because of ‘snaps’ – the universal package management system developed by Canonical. Snap applications are mounted as loop devices, hence constituting the various loop partitions you see in your system.

Can Loop Partitions be Deleted?

Technically, you could delete these loop devices to save space. This can be done using the ‘losetup’ utility. However, as these partitions are part of the snap system, deletion can cause problems with the running of snap applications, as snaps rely on these virtual partitions for their function.

Inspecting Loop Devices in Ubuntu

1. Listing Active Loop Devices


$ sudo losetup -a
/dev/loop1: [65025]:3574327 (/var/lib/snapd/snaps/core_15925.snap)
/dev/loop0: [65025]:3539127 (/var/lib/snapd/snaps/core_15511.snap)

Description: This command displays all active loop devices and their associated backing files. The output shows the loop device path, the associated file, and any relevant loop device attributes.

2. Identifying the Backing File Type


$ sudo file /var/lib/snapd/snaps/core_15511.snap
/var/lib/snapd/snaps/core_15511.snap: Squashfs filesystem, little endian, version 4.0, xz compressed, 123973296 bytes, 12906 inodes, blocksize: 131072 bytes, created: Sat May 27 09:09:52 2023

Description: The file command is a utility that determines the type of a given file. When applied to the backing file of a loop device, it can reveal whether the file is, for example, an ext4 filesystem, an ISO image, or something else.

3. Viewing File System Details of Loop Device


$ sudo fdisk -l /dev/loop0
Disk /dev/loop0: 118.23 MiB, 123973632 bytes, 242136 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Description: fdisk is a disk partitioning utility. With the -l option, it lists the partition tables for the specified devices. When run on a loop device, it can provide details like the filesystem type, the number of sectors, and the size of the loop device.

4. Checking Mounted Loop Devices and Their Usage


$ df -h | grep '/dev/loop'
/dev/loop0               119M  119M     0 100% /snap/core/15511
/dev/loop1               106M  106M     0 100% /snap/core/15925

Description: The df command reports the amount of disk space used by filesystems. The -h flag makes the output human-readable by using sizes in MB, GB, etc. Piping the output to grep '/dev/loop' filters it to show only loop devices. This can help you quickly see which loop devices are mounted and their disk usage statistics.

By using these commands, you’ll be able to inspect and manage loop devices on Ubuntu with more clarity and precision. Always remember to replace placeholders with the appropriate values for your specific context.

In Conclusion

It’s essential to understand the function of the loop partition within Linux system architecture. They can appear redundant and space-consuming to some users, but they play a critical role in the way certain applications operate, particularly snap apps. While it’s possible to delete them, it’s recommended not to, without a full understanding of the implications. After all, these partitions contain crucial components central to the operating system’s smooth functioning.