Debian – cron job not running the script that start vncserver

Here's what I did, and it seems to work in this situation. At least, it shows me an error, whereas running from the command line as the user doesn't show the error.

Step 1: I put this line temporarily in the user's crontab:

* * * * *   /usr/bin/env > /home/username/tmp/cron-env

then took it out once the file was written.

Step 2: Made myself a little run-as-cron bash script containing:

#!/bin/bash
/usr/bin/env -i $(cat /home/username/tmp/cron-env) "$@"

So then, as the user in question, I was able to

run-as-cron /the/problematic/script --with arguments --and parameters

This solution could obviously be expanded to make use of sudo or such for more flexibility.

Hope this helps others.

A few things occur to me while reading this.

If you are running bash echoing the value of $BASH should expand to the full path and filename of the bash executable in use.

How are you calling date in your script. Are you calling it with the full path name or as "date". The later case can result in the use of function, aliases, or whatever happens to be first in the path rather than the date program you expect.

Bash will behave differently in some cases depending on the environment. You may want to dump the environment to a file from the script and look at it running from the command-line and from cron. You may find that the PATH is different or that some other environment variable is set differently. You should be able to dump this to a file in /tmp by putting a line like "env > /tmp/environment.$$" in the script. Each time the script is run it will print out the environment to a file named environment.(pid of script)

You can set also the shell for the entire crontab to whichever shell you want by using "SHELL=/path/to/new/shell" on a line by itself.