1.poweroff
Description: Linux system can be shut down, off the record is written to / var / log / wtmp log file
Command syntax: poweroff [Options]
Option Meaning:
-n: Do not sync before closing
-p: power is turned off when the halt is called
-v: increase the output, a message comprising
-q: reduce output error messages only
-w: do not actually shut down the system, just write / war / log / wtmp file
-f: Force off, do not call shutdown
2.ctrlaltdel
Function: function may be provided by the Ctrl + Alt + Del key combination. ctrlaltdel has two support functions: hard and soft. hard to hard reset and immediately restart the computer without calling sync. soft bit soft reset, it sends the SIGINT (interrupt) signal to the init process. If you use a soft, init must support this feature
Command syntax: ctrlaltdel [hard | soft]
3.shutdown
Function Description: You can safely shut down or reboot the Linux system. Use the shutdown command before the system shutdown, the system administrator will notify a warning message to all logged-on user, the system will tell them to shut down, and the login process will be frozen, that new users can not log on. Direct shutdown or delay certain amount of time and then shut down is possible, may also restart. shutdown command also allows the user to specify a time parameter, the parameter can be a precise time, the start time from a time now. When the exact format hh: mm, the hour and minute, the time period represented by "+" and the number of minutes
Command Syntax: shutdown [options] [time] [warnings]
Option Meaning:
-k: do not execute shutdown, but a warning message to all users
-r: Reboot the system
-h: Shut down the system
-c: cancel running shutdown