Chapter 2. Building a Linux Gateway on a Single-Board Computer

2.0. Introduction

Linux lends itself so readily to hacking on old hardware we often forget it is not always the best hardware to use. While it is good to keep old PCs out of landfills, there are disadvantages to using them as routers and firewalls. They’re big, they use a lot of power, and they’re noisy, unless you have something of sufficient vintage to run fanless. Old hardware is that much closer to failure, and what do you do if parts fail? Even if you can find new parts, are they worth replacing?

Single-board computers (SBCs), like those made by Soekris Engineering ( and PC Engines ( are great for routers, firewalls, and wireless access points. They’re small, quiet, low-power, and sturdy. You’ll find information on single-board computers and other small form-factor computers at the Single Board Computer (SBC) Quick Reference Guide (

This chapter will show you how to install and configure Pyramid Linux ( on a Soekris 4521 board. There are many small distributions designed to power routers and firewalls; see Chapter 3 for more information on these, and to learn how to build an Internet-connection sharing firewall.

Despite their small size, the Soekris and PC Engines boards are versatile. PC Engines’ and similar boards all operate in pretty much the same fashion, so what you ...

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