How to build your own console server

Console Server

Gregory Bond

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$FreeBSD: doc/en_US.ISO8859-1/articles/console-server/article.sgml,v 1.23 2006/08/29 07:38:22 blackend Exp $

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This document describes how you can use FreeBSD to set up a “console server”. A console server is a machine that you can use to monitor the consoles of many other machines, instead of a bunch of serial terminals.

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Table of Contents

1 The Problem

2 Possible Solutions

3 Our Solution

4 Setting Up The Server

5 Cabling

6 On Sun Systems And Break

7 Using a Serial Console on FreeBSD

8 Security Implications

9 On Conserver Versions

10 Links

11 Manual Pages

1 The Problem

You have a computer room with lots of UNIX? server machines and lots of communications hardware. Each of these machines needs a serial console. But serial terminals are hard to find and quite expensive (especially compared to a much more capable PC). And they take up a lot of precious space in the computer room.

You need access to the console because when things break, that is where error messages go. And some tasks have to be done on the console (e.g. boot problems or OS installs/upgrades). Some UNIX systems allow the console to break out to the ROM monitor which can sometimes be the only way to unstick a hung machine. This is often done with a LINE BREAK sent on the console serial port.

If we are going to play about with consoles, then there are a couple of other things that would be great:

• Remote access. Even in the same office, it would be convenient to access all the consoles from your desk without walking into the computer room. But often the machines are off-site, perhaps even in another country.

• Logging. If something has gone wrong, you would like to be able to have a look at the previous console output to see what is up. Ordinary console screens give you the last 25 lines. More would be better.

• Network Independence. The solution needs to work even if the network is down. After all, a failed network is when you need consoles the most! Even better is network independence with remote access.

• No single-point failure. A console system that crashes every machine when it fails is no use. This is particularly tricky with Sun UNIX hosts as they will interpret a powered-off terminal as a BREAK, and drop back to the ROM monitor.

• Interface with a pager or some similar alerter device.

• Ability to power-cycle machines remotely.

• Not be too expensive. Free is even better!

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