Dyndns is a free dynamic DNS service. It allows people who doesn't own a fix public IP address to be DNS resolved.
This page describe how to use ddclient to update dyndns records.

Add the package :

• ddclient

During the installation, a set of questions are asked, if you want to redo it :

dpkg-reconfigure ddclient

The config of ddclient is stored inside /etc/ddclient.conf.

Example :

# Configuration file for ddclient generated by debconf
#
# /etc/ddclient.conf

protocol=dyndns2
use=if, if=eth0
server=members.dyndns.org
login=votrelogin
password='**********'
mx=votre.server.mx
backupmx=yes|no
wildcard=yes
monadresse.dyndns.org

Some explanation of those parameters :

• protocol : several protocols are available, each one use specific options, see http://ddclient.sourceforge.net/?page=2
• use : define how to get the public IP (see http://ddclient.sourceforge.net/?page=3)
  • use=if, if=eth0 use the IP of interface eth0
  • use=web, web=checkip.dyndns.com, web-skip='IP Address' get the IP from a website
• login : dyndns account
• password : dyndns password
• mx (optional) : MX server
• backupmx (optional) : if this option is enabled, the MX record will be used as a backup if the main IP is unreachable
• wildcard (optional) : all hosts below your DNS name will be resolved with the public IP
• Add your aliases as the send

To use ddclient with OVH service, configure ddclient for dyndns and change this line :

server=www.ovh.com

The update can be done by https (version > 3.7) with the ssl option :

ssl=yes

ddclient only allow to update one public IP. With 2 internet lines, I needed to create a second instance of ddclient.
Moreover this instance use an SNMP request on a Juniper firewall to get the IP.

The SNMP OID for the IP is .1.3.6.1.4.1.3224.9.1.1.6.5. The package “snmp” needs to be installed to get this value.

To create a second instance of ddclient, follow the steps :

• Create a second configuration file /etc/ddclient2.conf :

# Configuration file for ddclient generated by debconf
#
# /etc/ddclient2.conf

pid=/var/run/ddclient2.pid
protocol=dyndns2
use=cmd
cmd="snmpget -Oq -Ov -v 1 -c public 192.168.10.254 .1.3.6.1.4.1.3224.9.1.1.6.5"
server=members.dyndns.org
login=votrelogin
password='**********'
wildcard=yes
mx=votre.server.mx2
backupmx=yes|no
monadresse2.dyndns.org

• copy /etc/init.d/ddclient as /etc/init.d/ddclient2 and add it on startup :

# cd /etc/init.d
# cp ddclient ddclient2
# update-rc.d ddclient2 defaults 20
 Adding system startup for /etc/init.d/ddclient2 ...
   /etc/rc0.d/K20ddclient2 -> ../init.d/ddclient2
   /etc/rc1.d/K20ddclient2 -> ../init.d/ddclient2
   /etc/rc6.d/K20ddclient2 -> ../init.d/ddclient2
   /etc/rc2.d/S20ddclient2 -> ../init.d/ddclient2
   /etc/rc3.d/S20ddclient2 -> ../init.d/ddclient2
   /etc/rc4.d/S20ddclient2 -> ../init.d/ddclient2
   /etc/rc5.d/S20ddclient2 -> ../init.d/ddclient2
#

• then edit /etc/init.d/ddclient2 and change the following line :

OPTIONS="-daemon $daemon_interval -syslog -file=/etc/ddclient2.conf"

To check if it's working :

/etc/init.d/ddclient2 start

• /etc/ddclient.conf
• /etc/ddclient2.conf
• /etc/init.d/ddclient2

• www.dyndns.org
• http://ddclient.sourceforge.net/