Maximum Linux has a tutorial about booting into maintenance mode: "Maintenance mode is rather simple, yet extremely effective. Its sole mission is to
provide you, the home or corporate Administrator, the opportunity to boot into your
Linux box to make modifications to your operating system, without the annoyance of
other users logging in at the same time. Hence, this is why people often refer to
Maintenance mode as Single-User mode."
November 3, 2000