Purpose
I wanted to be able to just turn my laptop on and have it automagically figure out what network it was connected to as well as setting everything up that needed to be set up.
I also became quite annoyed at waiting for (or ctrl-c) eth0's dhcp to timeout whenever the cable wasn't plugged in. Basically, I wanted it to figure out for itself whether or not a cable was plugged in.
I've seen all kinds of laptop-wandering programs around, but I knew that ifupdown was the real tool to handle this sort of thing. Unfortunately, ifupdown is also rather confusing and almost completely undocumented. Here's my attempt to clear up some of the fog.
Platform
I figured out everything offered here under Debian / Testing on my VPR Matrix 220a5 in a couple hours between classes
Solution
To set up mapping, the interfaces(8) man page offers this example:
auto lo eth0 iface lo inet loopback mapping eth0 script /usr/local/sbin/map-scheme map HOME eth0-home map WORK eth0-work iface eth0-home inet static address 192.168.1.1 netmask 255.255.255.0 up flush-mail iface eth0-work inet dhcp
The main problem with this example is that it doesn't work. More specifically, the mapping lines don't work. The map line is supposed to take the "HOME" or "WORK" output by the map-scheme and given that run the appropriate eth-[whatever] block. It doesn't do this. What it does do is complain:wlan0=SCHOOL interface not foundor something along those lines. It's dumb. Anyway, as the best way to learn just about anything is by example, here are my /etc/network/interfaces, map-scheme, and my script which checks link status before attempting to bring up an interface.
Last updated: Sunday, 20-Sep-2009 16:55:45 CDT
Contact me at randall dot will at gmail dot com
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