[PROBLEM]
I've added individual crontab entries to several users. Each in their own crontab, using the officially documented and suggested method of "crontab -e" instead of editing root's global crontab in "/etc/crontab".
I've verified the following:
- Check if crontab entries per user are in place: "sudo crontab -u <username> -l"
- Check and restart crond: "sudo /etc/init.d/cron restart"
Nothing. The per-user crontabs were simply ignored.
[SOLUTION]
I forgot to add a blank newline at the end of each user's crontab.