My question is, how can I modify the script so that it will tell me what goes wrong?

The scenario is this: I'm trying to get Sonatype Nexus to start as a service in Ubuntu 10.04, and it just will not work.

(I'm not looking for help on how to run Nexus, but on how to get some useful output from a script)

It works when invoking it with

sudo /etc/init.d/nexus start

but fails when using

sudo service nexus start

I have run the update-rc.d command on it, and done everything according to instructions.

The nexus init.d-script has a point where it calls itself when it detects that it should run as another user ('nexus'):

su -m $RUN_AS_USER -c "\"$REALPATH\" $2"

which expands to

su -m nexus -c '"/opt/nexus-2.0.2/bin/jsw/linux-x86-64/nexus" start'

when adding the -x debug flag to the script. This command results in return code 1. It never executes - I've set -x debug flag on the script, placed echo commands with redirect to file at the start of script to trace, etc.

I cannot get any output telling me why the command will not execute. I've tried appending redirect to file after the above script line, inside the quotes, outside, any way I could imagine. All info I can get is by inserting a line

echo $?

after the su line, which outputs '1'.

Is there a way I can see what happens when the su command runs?