Sometimes you want to use an ISO image (of a CD or DVD) without having to burn it to a disc first. Here's how:
1) You need to make the directory to put the ISO into using the following command (you can name the directory whatever you prefer):
sudo mkdir /media/isoimage
2) You may need to add the loop module to your kernel. It was already loaded on my system, but if you need to do this, type the following command:
sudo modprobe loop
What is the kernel loop module and what does it do? I don't know. You'll have to ask someone else for that.
3) Mount the ISO image:
sudo mount mydisc.iso /media/isoimage/ -t iso9660 -o loop
Now your ISO should be mounted and accessible in the directory you specified.
sudo umount /media/isoimage/