User Notification of System Down Time

When the shutdown command is initiated, a warning followed by a final shutdown message is broadcast to all users who are currently logged onto the system and all systems that are mounting resources from the affected system.

For this reason, the shutdown command is recommended over the init command when you need to shut down a server. When you use either command, you might want to give users more notice by sending them a mail message about any scheduled system shutdown.

Use the who(1) command to determine which users on the system need to be notified. This command is also useful for determining a system's current run level. See How to Determine a System's Run Level.