Linux wall Command Tutorial for Beginners (with Examples)

There are times when multiple users are logged in to a server computer, and you - the system/network admin - need to, say, restart the server to perform some maintenance task. Of course, the correct way is to inform all those who are logged in about the maintenance activity. Thankfully, Linux offers a built in command line utility for this purpose, the wall command.

Source: Howtoforge Linux Howtos und Tutorials