Using CentOs, I want to run a script as user 'training' as a system service. I use daemontools to monitor the process, which needs a launcher script that is run as root:

1. :

   #!/bin/bash
   exec >> /var/log/training_service.log 2>&1
   setuidgid training training_command
   

   This last line is not good enough since for training_command, we need environment for training user to be set.

2. :

   su - training -c 'training_command' 
   

   gives 'standard in must be tty' as su making sure tty is present to potentially accept password. I know I could make this disappear by modifying /etc/sudoers a la Bash & 'su' script giving an error "standard in must be a tty" but i am reluctant and unsure of consequences.

3. :

   runuser - training -c 'training_command' 
   

   gives runuser: cannot set groups: Connection refused. I found no sense or resolution to this message.

I am stuck. Is this something so hard to achieve?

I appreciate all insight and guidance to best practice.