Unix Cron : Can we set cron jobs to run at the same time

Cron can run many scripts at the same time. In fact, in Debian there are entire directories of cron scripts (ie. /etc/cron.daily /etc/cron.hourly) that execute at the same time.

If the script executes properly at a different time, why don't you try changing the time of the root cron job to determine whether the problem is with the actual timing, or a conflict between the scripts.

I also agree with turning off the redirect to /dev/null until you have everything working correctly.

That crontab you posted is set up to only run at 00:05 the 10th every month, is this what you wanted?

Please check that your script in /opt has executeable permissions, and that it's prorperly calling up sh. You can try this by simply running the script in the console (by using its full path, dont put "sh" in front of the command)

Try to check the directory /var/spool/cron/ for your username, the cron file should be there (somewhere - I don't have access to a system right now).

I would take the /dev/null redirect off of the job and have cron email you the output of the file. It could be the script has a problem (maybe assuming an environment variable that doesn't exist when running through cron).