Notifying Users of System Down Time

When the shutdown command is initiated, it will notify all logged-in users and all systems that are mounting resources from it of the impending shutdown with a warning and then a final message.

This is why the shutdown command is recommended over the init command when used on a server. When using either command, you may want to give users more notice by sending 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, which is described on "How to Determine a System's Run Level".