How Can I Test That an ISO File Works?

Open a terminal, and then go to the folder where the ISO image has been downloaded. As an example, if you saved it to your disk in Firefox, it will have saved it to the Desktop folder in your home folder:

foo@bar:~$ cd Desktop

To test that the ISO image works, you are going to mount it and access the files in a particular folder. First, create this folder:

foo@bar:~$ mkdir test_iso

Now mount it on that folder:

foo@bar:~$ sudo mount -o loop -t iso9660 my_iso_file.iso test_iso

That's it! Now you can browse the folder test_iso.

Verifying the ISO

To verify the iso, fire up a terminal, and run the following command:

foo@bar:~$ md5sum my_iso_file.iso

Wait a little while and Ubuntu will print a "word" that is 33 characters long. Now go to the site  from which you downloaded the file, and compare this word with the md5sum given by the owner of the iso file, usually a file named MD5SUMS. The words should match.