So, let’s say you installed Linux on a flash drive or external hard drive and now you can’t boot into it, it might say it can’t boot or find /dev/sda3, this usually means that the distro installed using the /dev names, which can change system to system, even between boot-ups. Most distros I have come across set the fstab to look for “/dev/sdX#” we don’t want that, because the removable media might not be in that spot on every system so how do we do it? With UUID’s, or Universally Unique IDentifiers.
I should say right now, there may be other problems, this is just one possible fix to get it to run between systems.
The first thing we need to do is mount the system on the drive you want to use, so you are going to need a live CD or another Linux system to make this work. We’re going to pretend my system needs this. So first we will mount the root system known as “/” (/dev/sda3 for me) and then mount /boot. (We will need to be root for all of this) so: