If your Linux (Mint) fails to boot because you broke the /etc/fstab, for example, you’ll end up with a ready only root shell. The trick is to mount the root partition to as read-write without actually unmounting it:
# mount -o remount,rw /After doing that, you wil be able to edit /etc/fstab, correct the error, and reboot normally.
Found on: How to fix Linux boot problems