cron problems

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# 1  
cron problems

I am trying to setup a cron that runs a script to update my ip for my domain name every time I reboot and checks if my ip changes every 5 minutes and if it does then I update it. I am running Ubuntu server 12.04.

The file /etc/cron.d/ipupdate contains
#  Run ipupdate

/5 *     * * *     root         /usr/local/bin/ipupdate
@reboot            root         /usr/local/bin/ipupdate

The file /usr/local/bin/ipupdate contains
#Script to enable dynamic IP
if [ `ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}'` != `cat /usr/local/bin/ipchange` ]
wget -q -O /dev/null
ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}' > /usr/local/bin/ipchange
echo `date` IP updated to `cat /usr/local/bin/ipchange` >> /home/foo/log
echo `date` IP update finished running >> /home/foo/log

and the /etc/cron.d/ipchange just contains the ip from the last change.

All the above files have been set to give permission to all users (chmod 777) and when I run the script with /usr/local/bin/ipupdate it works how I want it to.
# 2  
first thing to try when cron is misbehaving is to provide a full pathname to any executables, eg /sbin/ifconfig
This User Gave Thanks to Skrynesaver For This Post:
# 3  
What is in /home/foo/log? The last line of your script should always update that file, even if the if block doesn't execute.

If that log doesn't get updated, it's probably a permission problem.
This User Gave Thanks to ThomasMcA For This Post:
# 4  

It is working now. I think the problem was that the change file did not belong to the root user.

Thanks for all the help

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