shutdown

Power off immediately

$ shutdown -h now

$ shutdown -r now

$ shutdown -r +5 &

$ shutdown -h 13:00

$ shutdown -c

shutdown [options] [time] [message]

shutdown brings the system down in a safe way. All logged-in users are notified, new logins are blocked, and running processes are signaled to terminate gracefully.
The time argument specifies when to shut down: now for immediate, +m for minutes from now, or hh:mm for a specific time. An optional message can be broadcast to all users.

-h, --halt

Halt the system after shutdown

Power off the system (default with -h)

Reboot the system

Cancel a pending shutdown

Send warning message but don't actually shutdown

Execute immediately

Execute in m minutes

Execute at specified time (24-hour format)

Requires root privileges. Scheduled shutdowns can be cancelled with -c. On systemd systems, this command is typically a wrapper around systemctl poweroff/reboot.

The shutdown command originated in early Unix systems. It evolved from a simple system halt to a comprehensive tool for graceful system shutdowns with user notification.

reboot(8), halt(8), poweroff(8), systemctl(1)