HowTo: Shutdown Linux System

'm new to Linux operating system. How do I shutdown Linux system using command line options?

The recommend and secure way to shutdown Linux desktops, Laptops, routers, and server is to use the shutdown command. Another option is to use halt or poweroff command. The syntax is as follows for the shutdown command:

 
shutdown -h time "message"
 

Where,

• -h : Poweroff the system.
• time: When to shutdown. You can poweroff imediatly or after 2 minutes. It can be an absolute time in the format hh:mm, in which hh is the hour (1 or 2 digits) and mm is the minute of the hour (in wo digits). Second, it can be in the format +m, in which m is the number of minutes to wait. The word now is an alias for +0.
• message: Send warning message to send to all users.

Steps to shutdown system

First, open a command-line terminal (select Applications > Accessories > Terminal). For remote system, login using ssh. Next, switch to the root user by typing su - and entering the root password, when prompted.
Finally, the following command to shutdown system immediate as root user:
# shutdown -h now
OR
# shutdown -h +0

Task: Shutdown with warning message

To shutdown system in 10 minutes with the following warning message:
# shutdown -h +10 "Development server is going down for maintenance. Please save your work ASAP."
Sample outputs:

Broadcast message from root@wks01 (pts/0) (Sat Apr 21 02:26:30 2012):
Development server is going down for maintenance. Please save your work ASAP.
The system is going DOWN for system halt in 10 minutes!

Say hi to poweroff command

You can halt the system, switch off the power. This is called as poweroff and poweroff command can be used as follows (warning: the following command will immediately shutodown the Linux system):
# poweroff

Task: See log of system shutdown

The last reboot or last shutdown command will show a log of all reboots and shutdown since the log file was created under Linux:
# last reboot
OR
# last shutdown
# last -x shutdown
Sample outputs:

shutdown system down  2.6.32-131.12.1. Sun Jan  1 05:03 - 05:05  (00:02)
shutdown system down  2.6.32-131.12.1. Sun Aug 28 16:53 - 17:00  (00:06)
shutdown system down  2.6.32-131.12.1. Sat Aug 27 17:21 - 17:23  (00:02)
shutdown system down  2.6.32-131.0.15. Sat Aug 27 17:15 - 17:18  (00:02)
wtmp begins Sat Aug 27 17:08:12 2011