The NetworkManager program in linux has a create feature called a dispatcher, which can run arbitrary programs when certian things about the network change. For instance it can turn on a firewall or notify a user when the network comes up, or start up an arp alert program!

I wanted a program that would alert me of my laptop’s where-a-bouts, as well as use the webcam to take a picture, in order to aid me in tracking it down if it got stolen. I wanted something simple and didn’t way to pay for anything… I know I’m cheap :)

The code is pretty simple:

    fswebcam -F 2 -S 1 -r 640x480 --jpeg 60 --save /tmp/capture.jpg
    ifconfig > /tmp/ifconfig.txt
    wget -q -O - checkip.dyndns.org >> /tmp/ifconfig.txt
    FILENAME=`date +%F-%H-%M-%S`
    mv /tmp/ifconfig.txt /tmp/$FILENAME.txt
    mv /tmp/capture.jpg /tmp/$FILENAME.jpg
    scp /tmp/$FILENAME.jpg /tmp/$FILENAME.txt root@X.0.0.0:OBSCURED FOR SECURITY REASONS
    rm /tmp/$FILENAME.jpg /tmp/$FILENAME.txt

You can see that it takes a picture, grabs my ifconfig and public ip, then ships it all to my server.  I just saved it in my /usr/local/bin/ and added the program to my /etc/network/if-up.d/openvpn program. This program is called whenever the interface comes up, so it will also run this program too when it’s ready.

It’s not amazing, but its good. Feel free to take my script and adjust for your needs. You may have a different command-line tool to take a picture with your webcam or whatever. You could even go crazy and setup something to email you or whatver, its YOUR program!