Slight variation to the solutions above. I was having a similar problem getting the mythconverg_backup.pl script to run daily. I realize there is a weekly DB backup script in cron.weekly but I wanted it to run daily and I wanted to use the mythconverg_backup.pl script since it appears to be the most elegant DB restoral path.
Including it in cron.daily didn't get it to run. Was going to follow suggestion above to specify the user (ie not root user) in the /etc/crontab file but this page suggests that may be overwritten on updates, so I did as suggested on that page and entered the job with 'crontab -e' so that my local user crontab looked like this:
... where the /etc/cron.daily/mythconverg-backup-mytry file was :
# m h dom mon dow command
20 04 * * * /etc/cron.daily/mythconverg-backup-mytry
I don't know if the PATH and SHELL entries are needed, I added them to be safe...and I suspect I could have simply referenced the actual perl script directly or copied it into the daily directory, but anyway, after setting the time in the crontab to run a few minutes into the future to test I was overjoyed to find a brand new backup in the right location a few minutes later. So thanks for the solutions in this threal
Just found out the 'gnome-schedule' app provides a gui for crontab as well, if that is your thing...