Linux Loop Devices and How to Use Them

If you're a Linux user, you might have stumbled upon the /dev directory that exists in the root directory of your Linux filesystem. There are many devices in the root directory that we will talk about in different blog posts. However, this blog post is dedicated to the loop devices. Whether you have heard about loop devices or stumbled upon them, this article is your guide to understanding what they do and how to use them.

What Are Linux Loops?

Linux loops are a series of devices that let you treat a file as if it were a block device. Whenever you mount and treat a file (most commonly a .iso file) like a physical disk or partition, one of the Linux loop devices is in use. Remember that Linux devices are not necessarily a part of your computer's hardware. Instead, there are some devices representing your hardware and some others representing device-like features of the Linux kernel. Moreover, we will talk about how and why everything is a file in Linux in a later post.

Where Are the Loop Devices?

In short, they are in the /dev directory. However, if you want to go and see them for yourself, you can use one of two methods:

Using the Graphical User Interface

You can open a new file browser window in your Linux and navigate to the root directory. There, you will see a directory named dev. Inside the dev directory are many files, each of which represents a device that your OS uses to perform different tasks. If you scroll down, you will see a list of loop devices named loop0, loop1, etc.

Using the Terminal

If you use a terminal command like ls to look inside the /dev directory, you will see that there are many files there, each of which represent a device that your OS uses to perform different tasks. In the /dev directory, you will see a number of loop devices. Mine are 34 and are named loop0 to loop33.

How Can I Use a Loop Device to Mount a File?

There is a special terminal command in Linux that helps create and set up loop devices. Using the losetup command, you can view all of the loop devices and what they are attached to, create new loop devices, and set them up to represent the file that you want.

Attaching and Mounting the Loop Device

To get started, you can take a look at all of the loop devices that are currently attached to a file by typing the following command into your command line (-a shows all attachments):

Next, you can mount the loop device into your /mnt folder using the following command:

Unmounting and Detaching the Loop Device

When you are done with your mounted file, you can then unmount it and detach the file from the Linux loop device. Here's how you can unmount the device:

Next, detaching the loop device from the file using a -d option:

Conclusion

In this article, we talked about what Linux loop devices are, where they are, and how you can use them. I hope this has been helpful for the Linux enthusiasts out there.

If you haven't checked my blog yet, check out my other posts! I am Farhang, a Linux and programming enthusiast, and I post every day.