//go to grub loader, press ESC, then highlight linux, click e to edit, then click e on the kernel line to edit again and add the word single to the end. ENTER then b to boot in single user mode. Once at command prompt.

mount -o remount,ro /dev/sdx //to go to read only
e2fsck -fy /dev/sdx //to repair file system
mount -n -o remount,rw /dev/sdx //to return to read write mode

mounting repair file system remount linux

Bash