Tutorials Linux DDNS Update Client wget

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Revision as of 02:21, 20 July 2009 by Raeb (talk | contribs) (initial version)
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This document contains instructions for setting up your Pre to automatically update a dynamic DNS hostname to your Palm Pre's IP address (assigned by your data service provider).

If you're using the Optware Package Feed you might want to check out ez-ipupdate or INADYN. However, if your dynamic DNS service isn't supported by either of these, you're building a custom service, or you want a freedns.afraid.org solution that doesn't require an always-on daemon, this guide may be for you.

This mechanism functions by adding a priority default routing rule that forces all traffic to go over the ppp0 (EV-DO) connection. This ensures we're updating your service with your ppp0 ip and not your eth0 (Wifi) ip. It optionally then finds your IP address from http://checkip.dyndns.org. Then, it calls your update URL. Finally, it removes the default route it created in step 1.


  • This page assumes that you have just finished the procedure on the Portal:Accessing_Linux page, and are still logged in as root via telnet, novaterm, or novaproxy.
  • This page assumes you have a Dynamic DNS service account with a service that provides URL based updating (i.e. http://freedns.afraid.org)

Enabling write access to the file system

 mount -o remount,rw /

Obtain the Update URL provided by your service

For http://freedns.afraid.org, log in, and find the 'Direct Update URL' for your dynamic DNS entry. Mine looks like this:


This updates the IP of my DNS entry to the IP of the client. We need to make sure we call this address from the Template:Ppp0 interface so that it updates to the correct IP. When the Pre is connected to a wifi connection, a default routing entry forces all data to go over that connection.

However, your service may differ, and require different information (example):


This example doesn't require the caller to be from the new target IP address, and won't need the routing entries.

Update your service whenever your ppp0 (EV-DO) IP address changes

You can do this by adding a script to /etc/ppp/ip-up.d called 09update-ddns.

This is the script for the first example shown above:

 export gateway=`ip route | tail -1 | awk '{print $3}'`
 ip route add default via $gateway dev ppp0 metric 1
 wget -qO- http://freedns.afraid.org/dynamic/update.php?ZzYyXxWwUuTtSsRr==
 ip route del default via $gateway dev ppp0 metric 1

This is the script for the second example. Note that it gets your IP address and stores it in $myip:

 export myip=`ifconfig ppp0 | head -2 | tail -1 | awk '{print $2}' | sed 's/[^1-9.]//g'`
 wget -qO- http://mydynamicdnsservice.com/?host=myhost.com&Ip=$myip

Make this script executable

 chmod 755 /etc/ppp/ip-up.d/09update-ddns

Remount the file system as readonly

 mount -o remount,ro /
  • by raeb
  • big thanks to dreadchicken's tutorial