System Recovery

Sometimes your system can get messed up in ways that may seem unrecoverable, however, Ubuntu has tools that can help. If you can successfully get to the GRUB menu (hold shift after you get past the POST screen), go down to the section starting with Advanced options. Then go to the first line ending with (recovery mode). You should be dropped into a TUI screen with multiple options.

Use the arrow keys to go up and down, and enter to choose your selection. If your in doubt, use the root option.