ISO images are often used to contain CD-ROM or DVD data, but Linux users will occasionally find themselves working with IMG files instead. These contain direct disk images, which can be worked with in a similar way. At one point these were generally used for writing an entire file system directly to a discrete diskette, but few people would ever wish to do that in today’s world. There are two major reasons modern Linux users would need to work with them, however. One is if an IMG file was used to distribute a driver or other piece of an operating system that needed to be restored. The IMG file can be mounted and the individual file from inside of it’s contained system could then be copied over to a booted file structure. The other reason, which is becoming extremely popular, is for working with virtual machines and other forms of hardware virtualization.
Linux provides several different ways to work with these contained structures. Depending on your distribution, you might be able to work with them in a purely graphical environment. The same CLI tools that mount ISO images could also mount IMG if this isn’t possible for you, however.
Method 1: Mount With Graphical Menus
If you’re using PCManFM or another file manager that supports mounting an image directly via the /media folder with a menu driven system such as some versions of Nautilus, then you should hold launch your manager to start. You’ll either need to launch this from the Panel Menu in LXDE or from the Applications menu in GNOME. Once you’re open, navigate to the Downloads folder by clicking the link in the left panel and then right click on the disk image you downloaded. It’s generally smart to have ensured that your browser didn’t detect any malware before proceeding.
Once the context menu appears, select the “mount disk image” option. The label for this command will change depending on your particular distribution. The image will automatically mount at /media/USERNAME/disk, with USERNAME being replaced with your actual user name. Click on the left panel of the file manager where it reads the size of the image in question. In our example we used an image of an older Linux distribution called tomsrtbt (pronounced Tom’s Root Boot), which fit an entire operating system in less than three megabytes. Hence the “2.9 MB Volume” label refers to the image in question.
You may now drag or right click and copy any of these files to any other section of your file system for safekeeping. When you’re done you can click on the X logo next to the label to close it. If you’re using a file manager that doesn’t support this method of unmounting an image, then start the GNOME Disks utility from the Panel Menu or the Applications tab. Click on the device that has the same name as the label from the file manager and then click on the square stop button to close down the file system.
Method 2: Via the Loopback Device
Disk images could be mounted via the loopback device as well, in much the same way as ISO images can be. This technique will be necessary if you use Thunar, Konqueror or any other file manager that doesn’t support direct mounting via graphical techniques. If you haven’t been able to mount an image graphically, then hold down CTRL, ALT and T at the same time. Type ls /mnt to make sure your /mnt directory is empty. If it’s not or if you don’t feel comfortable using it directly, then you can use sudo mkdir /mnt/toms to create a mountable directory. You could theoretically call the directory whatever you’d like. Type sudo mount -o loop tomsrtbt-2.0.103.ElTorito.288.img /mnt and press enter. You will be prompted to enter your password, which you will be required to do. The /mnt directory can then be explored via the CLI or the file manager you prefer. Naturally you’ll need to replace tomsrtbt-2.0.103.ElTorito.288.img with the image you’re using and /mnt with the directory tree segment you’re using.
Hold down CTRL and E to open your graphical manager or start it from the Applications or Whisker menu depending on which desktop environment you are using. Select the File System option from the left pain, navigate to /mnt and then select the /mnt folder. You’ll now be able to examine the contents of the image file.
At the CLI type sudo umount /mnt and press enter to umount the image. You would need to substitute whatever mount point you used for /mnt when you do so.