Wireless Hacks

Hack 53 Pebble

Use this tiny Debian-based distribution for your own custom wireless access point.

Terry Schmidt of NYCwireless has done terrific work in getting together a stripped down Linux distribution specifically tailored for wireless access points in general, and for the Soekris [Hack #51] platform in particular. This distribution is called Pebble, and is freely available at http://www.nycwireless.net/pebble/. It aims to balance functionality with size, weighing in at about 47 MB. As it is based on Debian, customizing the installed software is very straightforward. Unlike some very tiny distributions, it uses standard libraries and binaries. This significantly simplifies upgrades, and it means that custom packages don't have to be built from source and linked to custom, stripped-down libraries.

• Based on Debian GNU/Linux 3.0r1 (Woody)

• Linux Kernel 2.4.20 with IPv6 modules

• HostAP 0.0.2 and utils

• bridge-tools

• djbdns caching dns server

• NoCatAuth running as nonroot user, post 0.81 nightly

• openSSH server 3.4p1

• openSSL 0.9.6c patched

• pcmcia-cs

• ppp and pppoe

• Zebra 0.92a-5

There are also a number of shell niceties, including wget, elvis, tcpdump, perl, and even lynx. It runs well on every Soekris model, and will spawn a serial console on those machines (or any machine that has a serial port available). It runs on virtually any 486 class machine (or better) with at least 32 MB RAM. If you don't need all of the functionality provided in the standard distribution, you can easily strip out the components you don't need, to fit it into an even smaller space. For example, eliminating Perl, NoCatAuth, djbdns, and a couple of nonessential shell utilities will easily let Pebble fit on a 32 MB flash card (although since 128 MB flash cards are now selling for $20, perhaps this is something of a waste of effort).

If you are running from flash memory, one of the most useful features in Pebble is that it mounts the bootable medium read only, and creates a temporary RAM disk for its temporary files. This means that once it is configured, the flash is never written to, which considerably extends the lifetime of your flash.

Since it is based on Debian, you can easily install and remove packages using the standard apt-get utility. Pebble is under active development, with contributions from many interested embedded networkers. If you can spare the tiny amount of space required for Pebble, I highly recommend trying it for your own access point application.