Ubuntu changed to grub 2 and I often find myself looking up how to finagle my way into a single user shell.
Step 1. Hold the right shift to display the grub menu at boot time. Step 2. Select the correct kernel, press CTRL+e to edit the boot command. Step 3. Append the two directives Single init=/bin/bash Step 4. Press CTRL+x to boot and wait for the root prompt. Step 5. Remount / as read/write with the command: # mount -o remount,rw /
When you are finished, issue a
reboot -f unless you are fond of kernel panics.