Howto set up automatic dynamic DNS update using ddclient [Ubuntu]

Welcome

Does your ISP only offer you a dynamically allocated public ip-address through dhcp? You are not alone! Dynamic-DNS to the rescue! As we all may know, a DNS A-record i.e. example.com resolves to a particular ip-address i.e. 1.2.3.4. You normally set this record manually by logging in to your DNS-provider-account. However, if your ISP does not offer you a static ip-address it can be a hassle to run i.e. a webserver, should the ip-address suddenly change making your DNS-record point to a now obsolete address. Visitors lost in cyberspace. The way around this is to set up a deamon running on your server that regularly checks for changes in the ip-address, typically every 5 minutes, and make changes to your dns-account when needed. In this blog-post we will look at setting up ddclient for this purpose. We will use the Linux Ubuntu-distro when doing this. Let’s do it.

First install ddclient:

apt-get install ddclient

This will install and start a configuration wizard. Type in your data.

I choose “other” here since my dns-provider is not listed.

My NIC was named em1 which can be shown running the ifconfig command

That was the last entry, now I get this at the prompt when finishing:

update-rc.d: warning:  stop runlevel arguments (1) do not match ddclient Default-Stop values (0 1 6)

This warning can be ignored. Checking with sysv-rc-conf  we can see that the ddclient service is configured to be on for runlevels 2,3,4,5 as it should be.

root@ubuntu01:~# sysv-rc-conf --list ddclient
ddclient     1:off      2:on    3:on    4:on    5:on

Let’s check what /etc/default/ddclient now looks like

root@ubuntu01:~# more /etc/default/ddclient

# Configuration for ddclient scripts
# generated from debconf on Tue Jun 23 11:47:25 CEST 2015
#
# /etc/default/ddclient

run_ipup="false"

run_daemon="true"

daemon_interval="300"

Ok, so everything looks nice and dandy here. deamon-mode true and update interval check every 300 seconds (5 minutes). Now take a peek what we got in /etc/ddclient.conf

root@ubuntu01:~# more /etc/ddclient.conf
# Configuration file for ddclient generated by debconf
#
# /etc/ddclient.conf

protocol=dyndns2
use=if, if=em1
server=dns.loopia.se/XDynDNSServer/XDynDNS.php
login=creang.com
password='password_here'
creang.com,creang.se

Ok, so no using of ssl here, I want the deamon to use ssl when calling my dns-provider-account for security reasons, so I put that as well in the config file, also my dns-provider does only support system=custom

ssl=yes
custom=yes

Please note that the line use=if, if=em1 will check for any change in ip-address against the NIC. This is viable if you have the public-ip assigned directly to your network interface, like I have. If you are running your server behind a router/firewall using NAT-forwarding then you will want to configure the use of requesting a web-page in order to fetch your current public ip-address, like this:

use=web, web=dns.loopia.se/checkip/checkip.php, 
web-skip='Current IP Address:'

Now, all done!

Just restart the service with:

 root@ubuntu01:~# service ddclient restart

We can now see that the deamon is running just fine with the pstree -p command

ddclient running as process 1348, runs every 300 seconds, five minutes

root@ubuntu01:~# ps -ef|grep ddclient
root  1348  1  0 13:10 pts/0  00:00:00 ddclient - sleeping for 110 seconds

Should you want to re-run the configuration wizard, use this command:

dpkg-reconfigure ddclient

Double check that everything is working correctly with this command:

root@ubuntu01:~# ddclient -daemon=0 -debug -verbose -noquiet
...
DEBUG:    get_ip: using if, em1 reports 85.225.140.7
SUCCESS:  creang.com: skipped: IP address was already set to 85.225.140.7.
SUCCESS:  creang.se: skipped: IP address was already set to 85.225.140.7.