Here is the steps:
- First, you have to install Unetbootin. In Ubuntu, simply run the following command to install it:
If you're not using Ubuntu and Unetbootin is not in your distro official repositories, download it from HERE.
- In Unetbootin, select the "Diskimage" option, then browse for an ISO and under "Type" select "Hard Disk" and leave "/" for the "Drive", then click OK:
- Once Unetbootin finishes, restart your computer and select "Unetbootin" in the GRUB2 menu. If the Grub2 menu doesn't show up, press and hold the SHIFT key. Because Unetbootin extracts the ISO, you'll have to run it again when you want to boot a new ISO, even if it has the same name and is placed in the same location as the old one.
The next time you boot up Unetbootin it will ask you "remove the existing version of Unetbootin". This won't uninstall the program; it'll just remove its GRUB entry, so hit OK (unless you want to keep it there).