What is the command to halt the system in single-user mode?

The command to halt the system in single-user mode is "init 1." When executed, this command changes the runlevel of the system to single-user mode, which is a minimal mode used primarily for maintenance and recovery. In this mode, only the root user is allowed to log in, providing a safe environment to perform administrative tasks without interference from other users or services.

Single-user mode typically provides access to a command line interface without starting the usual multi-user environment, allowing for tasks like file system checks or troubleshooting network issues. The focus on minimal services running makes it a suitable choice for emergencies or system repairs.

While "halt" can stop the system immediately, it does not necessarily enter single-user mode but rather shuts down the system altogether. The "shutdown" command can also gracefully halt or restart the system but does not explicitly set the runlevel to single-user mode. The "reboot" command will restart the system rather than halt it, and it also does not engage single-user mode.

Therefore, "init 1" is the most appropriate command for entering single-user mode, balancing system maintenance needs with the safety and control necessary during such procedures.