Ubuntu – Running script in Crontab every 3 days once

Your final "EDIT 2" logfile shows that your postfix system isn't set up properly. When a cron script sends output to stdout or stderr (eg, any error messages in the script) , it sends an email (to root@localhost by default), and you need a working mail server for that to happen.

It looks very much like your script is failing for some other reason and is writing something to stderr or stdout, but because you don't have a working postfix setup you're losing that information. It's quite likely those error emails have the information you need to work out why your script is failing.

That, of course, is assuming this isn't your error: Aug 7 22:30:01 acsserver CRON[6336]: Mount of private directory return code [256]

Either way, you should fix your postfix setup.

There's an obvious mistake in your cron line: you redirect error output to /dev/null. Don't do this, and look at your mail to see what went wrong.

A common problem with cron jobs is that they get a very limited environment: your .profile is not read. You may need to define some environment variables for your script to run.

ADDED: You did:

cp -rf /opt/rrdtool-1.4.4/lib/perl/5.8.8/i386-linux-thread-multi/* /usr/lib/perl/site_perl

Bad idea! You should not put your own files in /usr (outside /usr/local). That area is reserved to the package manager. Sure, it's easy now, but you will run into trouble tomorrow (for example when you upgrade rrdtool), and it'll be hard to debug then.

Instead, do what people have been recommending and define the necessary environment variables in your script (or source ~/.profile); you need PERL5LIB (and perhaps others).