How to Shutdown Ubuntu Server
We can use either shutdown or poweroff command to shutdown Ubuntu
Server from the terminal.
The Ubuntu shutdown command requires a time parameter while poweroff command will power off the server immediately.
shutdown command
The Ubuntu shutdown command should use with -P(Capital P) Option and require timer(when to poweroff).
shutdown -P timer
We can power off the Ubuntu server immediately by Passing now as the timer. If we want we can add time delay to Ubuntu shutdown command with either +minutes or hh:mm format as a timer.
Examples
shutdown -P now
This will shutdown your Ubuntu server immediately.
shutdown +3min
Ubuntu Server Will be poweroff in three minutes.
shutdown 12:20
Server will be poweroff at 12.20 PM
You can press CTRL + C on keyboard to Cancel a pending shutdown
Example
As Above screenshot shows, Fist I issued the Ubuntu shutdown command to power off the Ubuntu server after Five minutes. But then I decide to cancel it by pressing the CTRL + C on the keyboard.
shutdown command in Ubuntu Linux needs root privileges , So either you need to be the root user or you should be a administrative user who can run commands with sudo.
Poweroff command
poweroff command in Ubuntu Linux does not have a timer option. So the server will stop immediately after you type the poweroff command in the Ubuntu terminal.
Telinit command
Telinit command in ubuntu use to change the runlevel and since the runlevel 0 is halt means, if we change the runlevel to 0 using telinit command server will be powered off.
telinit 0
In a Live System i would recommend to use the shutdown command with time delay instead of poweroff and telinit command, because you can cancel the pending shutdown if you want.