Shutdown command format of CentOS shutdown method

The shutdown command sends a signal to the init program, asking it to change the system run level runlevel to 0. The shutdown command can complete the following operations:

1. 1. Shutdown mode selection: Shut down or restart.
   2. Shutdown time selection: You can specify to shut down immediately or at a specific time.
   3. Shutdown alarm information: Before shutting down, the specified information can be sent to the logged-in user.
   4. Only display warning information: In some cases, some system maintenance or update operations need to be performed. During this period, you do not want other users to log in to the system to avoid data loss or other problems. In this case, you can use the shutdown command with appropriate parameters. to notify other users, but does not actually shut down the system.

So how to use the shutdown command? Should I execute shutdown directly or do I need to add parameters before executing it? "Man" anytime and anywhere is a good habit for learning Linux. You can also use shutdown --help to view how to use the command. In comparison, man shutdown returns a more detailed command explanation.

The simple syntax rules of the shutdown command are:

shutdown [-krhc] [时间] [警告信息内容]

Parameter Description:
• -k: It is not really a shutdown, it only sends a warning message to the logged in user
• -r: Restart the system immediately after shutting down all services in the system
• -h: After shutting down all services in the system, shut down immediately.
• -c: Cancel the shutdown command operation that is already in progress.
• Time: Specify the time for system shutdown! Without this parameter, the system automatically performs the shutdown operation after 1 minute by default.

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