I recently switched my home ISP serice from Cable to DSL, and have had a very positive experience, especially considering the huge reduction in cost. What got me particularly excited was the DSL modem provided by Qwest: an Actiontec GT701-WG. Not does it provide 802.11g access, but the folks at Actiontec (in their infinite wisdom) made no attempt at making it difficult to work on. Plus, I get it free for a year on loan from Qwest.
The device is based on Linux (big surprise, right?), kernel version 2.4.17, running on a MIPS processor with 14 megs of RAM (or so it appears). It comes with a very simple web-based interface, and, best of all, allows a user to bring up a remote shell using telnet. The root username and password can be reconfigured from the web interface to allow for better security.
So, playing with my new toy, I found an available firmware upgrade from Qwest. I installed it, rebooted, and waited for my Internet connection to come back online. No joy. While the lights on the box indicated everything was kosher, the DSL modem was not reachable over any network adapter (LAN, wireless, or USB), and therefore neither was the Internet uplink. And here's where my journey began.
Using the GTRecovery tool that came with the modem, I was able to go back to a known-good kernel, and restore my Intenet connection. But curiousity got the better of me, and I had to know what was wrong with the firmware upgrade. To find that out, I need to be able to attach to the modem's serial console.