As others already pointed out >https://help.ubuntu.com/community/Fstab >https://wiki.archlinux.org/index.php/Fstab >See fstab(5). I recommend to read one of the above links. Running man fstab in a terminal, that is what "fstab(5)" is for, might not be that helpful for you. Forget about /etc/mtab and grub.