Linux Server Hacks, Volume Two

Hack #76. Use a Serial Console for Centralized Access to Your Systems

Keep a secret backdoor handy for midnight emergencies.

Imagine the following scenario. It's 3 A.M., and you're the administrator on call. All of a sudden, you're jolted awake by the pager rattling itself off the side of your nightstand. A critical server isn't responding to network polls, and you're unable to SSH into it to determine what the problem is. You are now faced with a tough decision—no one wants to get dressed and head into the office at 3 A.M., but this server is essential to your company's online presence. What do you do? The good news is that with proper fore-sight and planning, you can avoid this kind of decision altogether with a console server.

A console server is a device to which you can connect the consoles of multiple systems. You can then connect to the console server to get easy access to any of those systems. Devices that enable you to connect multiple serial ports and quickly switch between them are readily available from many different vendors. A quick Google search for "serial console server" will list more potential vendors than you probably want to know about.

This hack explains how to configure your Linux systems so that they can use serial ports for console output rather than the traditional graphical displays that we're used to on Linux systems. Not only are serial consoles inexpensive compared to multiple graphical displays, but they are easy to access remotely and fast because there ...