Question

In my crontab file I execute a script like so (I edit the crontab using sudo crontab -e):

01 * * * * bash /etc/m/start.sh

The script runs some other scripts like so:

sudo bash -c "/etc/m/abc.sh --option=1" &
sleep 2
sudo bash -c "/etc/m/abc.sh --option=2" &

When cron runs the script start.sh, I do ps aux | grep abc.sh and I see the abc.sh script running.

After a couple of seconds, the script is no longer running, even though abc.sh should take hours to finish.

If I do sudo bash /etc/m/start.sh & from the command line, everything works fine (the abc.sh scripts run for hours in the background until they complete).

How do I debug this?

Is there something I’m doing that is preventing these scripts from running in the background until they are done?

Answer 1

The program(s) you’re starting might be expecting a terminal to send their output to, or receive input from.

If you set the MAILTO= variable, and you have a sendmail(-like) daemon installed, you will get an email with the error message(s) it prints, if there are any:

MAILTO=[e-mail]
01 * * * * bash /path/to/something.sh

Another way to debug would be to run the script from the command line, while redirecting all inputs and outputs:

$ sudo bash -c "foo.sh" > output_file 2>&1 < /dev/null

Also, the system log files (usually found in /var/log) might contain useful hints.