Debian : update a dynamic DNS

A bit of context : I have a bind 9 DNS allowing DNS updates from clients on the LAN (ok this is fairly insecure, but still my LAN is my home LAN composed of 4 machines … let’s say that’s good enough for me ! 🙂 )

The named.conf allows those updates with this config directive in the zone config block :
allow-update {mynet; };

and mynet is defined an acl directive to be my LAN.

Then you can update your DNS with the nsupdate tool with a syntax along the following lines :
spaghetti:~# nsupdate
> server
> update delete A
> update add 8000 A
> send
> quit

I was then looking for a place to hook a code snippet doing that update after an update via DHCP and I found the answer in A dynamic dns update client on Debian with dhcp3-client (many thanks dude !).

Here is the drill down :

  1. install the dhcp3-client package (apt-get install dhcp3-client ): this version has easy to use hooks before and after querying the DHCP server to get network config
  2. you can drop a script which will automate the nsupdate in “/etc/dhcp3/dhclient-enter-hooks.d” and it will get run right after network configuration (see the sample debug script for the variable which are available upon script execution, such as $new_ip_address)