ddns for linux / unix in a simple cron job

Here is a script to update your dynamic dns for linux / unix...


edit a script:



vi /root/ddns.sh



put in ddns.sh :



<br />#!/bin/sh<br />USER=<USER><br />PASSWD=<PASSWORD><br />DOMAIN=<doman.dns.com><br />WILDCARD=<ON|OFF><br />WGET=/usr/bin/wget<br />FIND=/usr/bin/find<br /># DynDNS Update Client for linux unix<br /># Based on http://www.nslu2-linux.org/wiki/HowTo/DynDNSupdate<br /># Version: 08/03/2006<br /># Look for err.ip<br />if [ ! -f /var/tmp/err.ip ]<br />then<br /># On err.ip not found.<br /># Set up err.ip for error logging.<br />echo "off" > /var/tmp/err.ip<br />fi<br /># Fetch current IP Address.<br />${WGET} --quiet http://checkip.dyndns.org/ --output-document=/var/tmp/now.ip;<br /># Verify the data is good.<br />PAT='Current IP Address: *[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*'<br />if grep -q "$PAT" /var/tmp/now.ip;<br />then<br /># On good IP data.<br /># Check for IP history.<br />if [ -f /var/tmp/old.ip ]<br />then<br /># On history found.<br />if [ "`cat /var/tmp/err.ip`" = "on" ]<br />then<br />echo "`date +%Y%m%d.%H%M%S` - not updated: Network connection restored." >> /var/log/ip_hist.log;<br /># Turn err.ip Off<br />echo "off" > /var/tmp/err.ip<br />fi<br /># Check for IP Change<br />if [ "`cat /var/tmp/now.ip`" = "`cat /var/tmp/old.ip`" ]<br />then<br /># On no IP change<br /># Check if 28 day refresh is needed.<br />${FIND} /var/tmp/ -name old.ip -mtime +28 -exec rm {} \;<br />if [ -f /var/tmp/old.ip ]<br />then<br /># On no refresh needed.<br /># Check for Next day.<br />if [ ! "`cat /var/tmp/day.ip`" = "`date +%x`" ]<br />then<br /># On day change<br /># Log entry<br />echo "`date +%Y%m%d.%H%M%S` - No update - `cat /var/tmp/upd.ip`" >> /var/log/ip_hist.log;<br />echo "`date +%x`" > /var/tmp/day.ip;<br />fi<br />else<br /># On refresh needed.<br /># Do a 28 Day refresh and Notify user with a distinguishable beep.<br />${WGET} --quiet "http://${USER}:${PASSWD}@members.dyndns.org/nic/update?hostname=${DOMAIN}&wildcards=${WILDCARD}" --output-document=/var/tmp/upd.ip;<br />echo "`date +%Y%m%d.%H%M%S` - Refresh - `cat /var/tmp/upd.ip`" >> /var/log/ip_hist.log;<br />echo "`date +%x`" > /var/tmp/day.ip;<br />cp /var/tmp/now.ip /var/tmp/old.ip;<br />fi<br />else<br /># On IP change<br /># Update DynDNS with new IP Address.<br />${WGET} --quiet "http://${USER}:${PASSWD}@members.dyndns.org/nic/update?hostname=${DOMAIN}&wildcards=${WILDCARD}" --output-document=/var/tmp/upd.ip;<br /># Log the IP change and notify user.<br />echo "`date +%Y%m%d.%H%M%S` - update - `cat /var/tmp/upd.ip`" >> /var/log/ip_hist.log;<br />echo "`date +%x`" > /var/tmp/day.ip;<br />rm -f /var/tmp/old.ip;<br />cp /var/tmp/now.ip /var/tmp/old.ip;<br />fi<br />else<br /># On No History<br /># Initialize client and Update DynDNS.<br /># Check err.ip status<br />if [ "`cat /var/tmp/err.ip`" = "on" ]<br />then<br /># Log Service Restoral.<br />echo "`date +%Y%m%d.%H%M%S` - not updated: Network connection restored." >> /var/log/ip_hist.log;<br />fi<br /># Set err.ip off<br />echo "off" > /var/tmp/err.ip<br />${WGET} --quiet "http://${USER}:${PASSWD}@members.dyndns.org/nic/update?hostname=${DOMAIN}&wildcards=${WILDCARD}" --output-document=/var/tmp/upd.ip;<br />echo "`date +%Y%m%d.%H%M%S` - initialization - `cat /var/tmp/upd.ip`" >> /var/log/ip_hist.log;<br />echo "`date +%x`" > /var/tmp/day.ip;<br />cp /var/tmp/now.ip /var/tmp/old.ip;<br />fi<br />else<br /># On IP read error<br /># Check err.ip status<br />if [ ! "`cat /var/tmp/err.ip`" = "on" ]<br />then<br /># On err.ip = off - Log read error.<br />echo "`date +%Y%m%d.%H%M%S` - not updated: read error on ip fetch" >> /var/log/ip_hist.log;<br />fi<br /># Set err.ip = On to allow only one error log on next run.<br />echo "on" > /var/tmp/err.ip<br />fi<br /># end<br /># Set the interval of the next IP check using a crontab entry.<br /># Once every 15 minutes is good for a home server.<br />



chmod 755 ddns.sh



then store your crontab:



crontab -l > /root/crontab.new



edit the /root/crontab.new and add the line:



*/15 * * * * /root/ddns.sh &>/dev/null



then load the new crontab:



crontab /root/crontab.new



Your done! ddns is all ready to go!