What do you need to know about the cron daemon?
The Cron Daemon. The cron daemon is the system process that runs scripted jobs on a pre-determined schedule. The crontab command is used to tell the cron daemon what jobs the user wants to run and when to run those jobs.
Why is my crontab daemon not working properly?
The first and foremost one is that your Cron daemon might not be working for some reason which will consequently cause your Crontab to fail. The environment variables of your system might not have been properly set up.
How to tell if something is wrong with cron?
There are several ways to find out what’s wrong with your system. Cron usually send mail to the user when there is something wrong. If you see the message “You have mail” use a mail client to check your inbox. Or, check in your home directory, there may be a file named dead.letter there.
Where is the cron log file on my computer?
On my computer the log file is at /var/log/cron/current (requires root access). If you have root access, you can stop the cron daemon and start it in debug mode. For example I would use (change fcron to the name of your daemon): Most likely, when cron fails, it generates an email to the user id of the cron job on that computer.
Where does the cron output get mailed to?
The fastest way to find out what is going on is to add some debugging to the cron job script. If you do nothing, then by default the cron output will be mailed to root@localhost (unless you have configured this to be different), so assuming you have root access, add some debugging information to the script, such as:
Why does crontab run twice in cron job?
For sure it’s not the crontab entry that’s causing it to run twice. The fastest way to find out what is going on is to add some debugging to the cron job script.
How to stop the Cron and AT commands work?
The correct way to add or change a cron entry is to log in or su to the userID and then issue the crontab -e command. If you have manually edited one of the files, you must stop the cron daemon and let it respawn (restart). To stop the cron daemon, follow the steps below: