Single-user mode

Single-user mode is a mode in which a multiuser computer operating system boots into a single administrator user, instead of the normal system. It is mainly used for maintenance of multi-user environments, including network servers, where operating on the normal system would be difficult or impossible – for example, some tasks may require exclusive access to resources that are shared, like repairing a broken filesystem used for a network share. This mode can also be used for security purposes, as network services are not run, eliminating the possibility of outside interference. On some systems, a forgotten superuser password can be changed in single-user mode, although not asking for the password in this case is viewed as a security vulnerability.