halt
halt, together with poweroff, reboot are commands you can run as root to stop the system hardware. Specifically, halt instructs the hardware to stop all CPU functions. These commands require superuser privileges. If you are not logged in as root, you will need to prefix the command with sudo or the signal will not be sent.
$ sudo halt
[sudo] password for xxx:
Options/Examples
halt -p
Invoking halt with option -p would instruct the halt command to instead behave as poweroff. poweroff is a terminal command that would allow a system administrator to shutdown the system.
$ poweroff --help
poweroff [OPTIONS...]
Power off the system.
--help Show this help
--halt Halt the machine
-p --poweroff Switch off the machine
--reboot Reboot the machine
-f --force Force immediate halt/power-off/reboot
-w --wtmp-only Don't halt/power-off/reboot, just write wtmp record
-d --no-wtmp Don't write wtmp record
--no-wall Don't send wall message before halt/power-off/reboot
halt --verbose
It would output slightly more verbose messages when rebooting, which can be useful for debugging problems with shutdown.
halt --help
It would print a short help text and exit.
halt [OPTIONS...]
Halt the system.
--help Show this help
--halt Halt the machine
-p --poweroff Switch off the machine
--reboot Reboot the machine
-f --force Force immediate halt/power-off/reboot
-w --wtmp-only Don't halt/power-off/reboot, just write wtmp record
-d --no-wtmp Don't write wtmp record
--no-wall Don't send wall message before halt/power-off/reboot
Exit Status
On success, 0 is returned, a non-zero failure code otherwise.