Mindstab.net

During the course of updating my home computer I rebooted it because of a kernel update. Later that week at work I went to connect to my home computer and discovered that it’s dynamic IP had changed and it’s DNS name was invalid.

So following common advice to “fix a problem two ways to prevent it in the future” I fixed the DNS, but I also wanted an automated way to track my computers when and if their IPs changed.

So the first thing I needed was shared place to store the IP information. Thinking about it I realized that Dropbox would work well for that. So all I needed was a simple script.

So the solution was to put a script that determined the IP of the computer in Dropbox and have cron on all the computers run it. Each user can call cron with

$ crontab -e

And I created a crontab directory that I could add more scripts to later if need be with and run them hourly with the following entry

0 * * * * cd /home/dan && run-parts Dropbox/cron

The script itself was a file called getip and it used whatsmyip.com’s automation detection script.

getip

#!/bin/sh 
 
wget -O /tmp/`hostname`.ip http://automation.whatismyip.com/n09230945.asp
tmp_file=/tmp/`hostname`.ip
dst_file=Dropbox/var/log/`hostname`.ip
if ! diff -q ${tmp_file} ${dst_file} > /dev/null  ; then
  `cp ${tmp_file}  ${dst_file}`
fi

Then I just created Dropbox/var/log and installed the crontab on all my computers, and volia, homebrew IP tracking for all my compters accessible to me from anywhere.