Dynamic DNS service
Dynamic DNS allows you to have a DNS name while your IP address changes frequently. You will need to register for an account with one of the dynamic DNS providers. This service is often provided freely.
More information:
Popular dynamic DNS registration sites:
Installation ipUpdate (dnsexit.com)
The interface uses an (unsecure) http protocol and it is strongly recommended to configure a different password (token) for this service. Logon at http://www.dnsexit.com and go to My Account -> Account profile -> IP Update Password.
WAN IP update script using Linux Upstart:
sudo /etc/init/dyndns-ip-update.conf
Contents:
# upstart script
#
# Copy script:
# sudo cp $HOME/Scripts/dyndns-ip-update.conf.sh /etc/init/dyndns-ip-update.conf
# Test with:
# sudo stop dyndns-ip-update
# sudo start dyndns-ip-update
# Check log:
# sudo cat /var/log/upstart/dyndns-ip-update.log
author "Wilbert Volkers"
description "Update WAN IP address at DynDNS service www.dnsexit.com"
#start when network is up
#does not seem wait for the network so implemented the retries
start on runlevel [2345]
stop on runlevel [!023456]
# write stdout to log in /var/log/upstart/dyndns-ip-update.log:
console log
pre-start script
logger "pre-start for dyndns-ip-update"
end script
post-start script
logger "post-start for dyndns-ip-update"
end script
script
echo "$(date '+%Y-%m-%d %H.%M.%S') dyndns : start ..."
# settings
host="wilbertvolkers.linkpc.net"
login="LOGIN"
passtoken="PASSTOKEN"
storedipfile="/opt/dyndns-ip-update.ip"
# get current IP using checkip.dyndns.com
# ${retries} retries, every ${retrywait}
retries=5
retrywait=5s
i=0
while [ ${i} -lt ${retries} ]; do
currentIP=$( wget --quiet --output-document=- http://checkip.dyndns.com | sed -ne "s/.*[^0-9]\([0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\)[^0-9].*/\1/p" )
if [ -n ${currentIP} ]; then break; fi;
i=$((i + 1))
echo "$(date '+%Y-%m-%d %H.%M.%S') dyndns : get IP, try ${i}/${retries} failed, waiting ${retrywait}"
sleep ${retrywait};
done;
echo "$(date '+%Y-%m-%d %H.%M.%S') dyndns : current IP = '${currentIP}'"
# get previous IP from file
storedIP="unknown"
forceafterdays=3
if [ -f "${storedipfile}" ] ; then
#force update if stored IP older then ${forceafterdays} days
storedipfiledate=$( stat -c %y ${storedipfile} | cut -d ' ' -f1 )
storedipdays=$(( (`date +%s -d $(date '+%Y%m%d')` - `date +%s -d ${storedipfiledate}`)/86400 ))
if [ ${storedipdays} -gt ${forceafterdays} ] ; then
storedIP="old"
else
storedIP=$(cat ${storedipfile})
fi
fi
echo "$(date '+%Y-%m-%d %H.%M.%S') dyndns : previous IP = '${storedIP}' (${storedipfiledate})"
# update the dyndns IP if needed
if [ "${currentIP}" = "${storedIP}" ] ; then
echo "$(date '+%Y-%m-%d %H.%M.%S') dyndns : update not needed"
else
updateurl="http://update.dnsexit.com/RemoteUpdate.sv?login=${login}&password=${passtoken}&host=${host}"
response=$( wget --quiet --output-document=- ${updateurl} | tail -1 )
echo "$(date '+%Y-%m-%d %H.%M.%S') dyndns : updated : ${response}"
echo ${currentIP} > ${storedipfile}
fi
echo "$(date '+%Y-%m-%d %H.%M.%S') dyndns : done."
end script
Test script with:
sudo start dyndns-ip-update
Check log:
sudo cat /var/log/upstart/dyndns-ip-update.log | tail -10
More information on Linux Upstart:
Installation ddclient (dyndns and others)
This client updates the DynDNS record automatically.
sudo apt-get install ssh libio-socket-ssl-perl ddclient
Follow the instructions. Additionally configure a longer update interval 'daemon=3600' and use SSL:
sudo gedit /etc/ddclient.conf
protocol=dyndns2 use=web, web=checkip.dyndns.com, web-skip='IP Address' server=members.dyndns.org login=**dyndns-login** password='**dyndns-pwd**' wilbertvolkers.dyndns.org daemon=3600 ssl=yes
View ddclient logging:
cat /var/log/syslog* | grep 'ddclient'
Test/force refresh:
sudo ddclient -force
Reconfigure and restart, you can edit the config file instead:
sudo dpkg-reconfigure ddclient sudo /etc/init.d/ddclient restart
Remarks
Note that when your IP address has changed, the ddcient needs to announce this to your dyndns service. Then it is still possible that the DNS you are using does not give you the new IP address, it may take some time before updates are routed through the DNS network.
