When I bought my first laptop computer one of the first things I did was run fips and create a couple partitions to install Slackware 4.0 Linux on it. Once I got every thing running including the PCMCIA network card I had also purchased I thought "This is it, it can't get any better" Then I took my laptop to the office and plugged it into the lan there and ran netconfig to install the right network setting to work at the office. Realizing I would have to do this again when I got home and plugged back into my LAN there I started wondering if there wasn't an easier way. I looked around the web for a while and didn't find what I really wanted so I pretty much figured OK I will just live with it for the time being. Then one day when I was poking around in the /proc filesystem I noticed something that looked really usefull. I noticed that the file /proc/1/environ listed the lilo boot image label that I had used to boot my computer. What follows is the way I came up with to exploit this information.

When I had first installed the PCMCIA modules on my computer I had to edit the /etc/pcmcia/network.opts file and now I decided this was the place to start. I made several copies of the file, one for each place I might plug into a network and named them accordingly...

network.opts.hostname1

network.opts.hostname2

etc...

Next I edited each file with the proper network information for that network connection so that is looked something like this (network addresses changed).

# Use DHCP? [y/n]
DHCP="n"

# Host's IP address, netmask, network
address, broadcast address
IPADDR="192.168.1.1"
NETMASK="255.255.255.0"
NETWORK="192.168.1.0"
BROADCAST="192.168.1.255"

# Gateway address for static routing
GATEWAY="192.168.128.1"

# Things to add to /etc/resolv.conf
for this interface
DOMAIN="mynet.com"
SEARCH="mynet.com"
DNS_1="192.168.128.10"
DNS_2=""
DNS_3="" 

Next I modified my /boot/lilo.message file so that it would display a menu of choices of my hostnames and I created matching entries in my /etc/lilo.conf file as shown below.
/boot/lilo.message

^L          #clears screen
Welcome to my laptop


Please choose your poison from the options below.


1 - Win98
------------------------------LINUX IDENTITIES --------------------------------


2 - Hostname1
3 - Hostname2
4 - Hostname3

Trying 207.227.252.197...
message=/boot/lilo.message
delay = 300
prompt
vga = 6

other = /dev/hda1
  label = 1
  table = /dev/hda


image = /vmlinuz
  root = /dev/hda2
  label = 2
  read-only


image = /vmlinuz
  root = /dev/hda2
  label = 3
  read-only


image = /vmlinuz
  root = /dev/hda2
  label = 4
  read-only

That done all that remained was to get the information from /proc and utilize it during the boot process. I decided the best place to do this would be the rc.pcmcia script in the /etc/rc.d directory. I added my code just under the "# Source PCMCIA configuration, if available" section after the fi command. Here is what I added.

#set up network options
BOOT_IMG=`/bin/cut -d= -f4 /proc/1/environ`  # parses the boot image label

case "$BOOT_IMG" in

   2) echo "Setting up Hostname1"
       cp /etc/pcmcia/network.opts.hostname1
       /etc/pcmcia/network.opts
       echo "hostname1.mynet.com" > /etc/HOSTNAME
   ;;

   3) echo "Setting up Hostname2"
      cp /etc/pcmcia/network.opts.hostname2
      /etc/pcmcia/network.opts
      echo "hostname2.mynet.com" > /etc/HOSTNAME
   ;;

   4)
      echo "Setting up Hostname3"
      cp /etc/pcmcia/network.opts.hostname3
      /etc/pcmcia/network.opts
      echo "hostname3.othernet.com" > /etc/HOSTNAME
   ;;

esac

/bin/hostname -F /etc/HOSTNAME