How to start a service at boot time in ubuntu 12.04, run as a different user?

Question

I have a server ClueReleaseManager which I have installed on a Ubuntu 12.04 system from a separate user (named pypi), and I want to be able to start this server at startup.

I already have tried to create a simple bash script with some commands (login as user pypi, use a virtual python environment, start the server), but this does not work properly. Either the terminal crashes or when I try to ask the status of the service it is started and I am logged in as user pypi ...?

So, here the question: What are the steps to take to make sure the ClueReleaseManager service properly starts up on boot time, and which I can control (start/stop/..) during runtime, while the service is running from a user pypi?

Additional information and constraints:

• I want to do this as simple as possible
• Without any other packages/programs to be installed
• I am not familiar with the Ubuntu 12.04 init structure
• All the information I found on the web is very sparse, confusing, incorrect or does not apply to my case of running a service as a different user from root.

Solution

A basic script to start a service could look like this:

#!/bin/sh

# This is for the 'update-rc.d', so it knows when to start your service.
### BEGIN INIT INFO
# Provides:          your-script
# Required-Start:    $all
# Required-Stop:
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: a short description
# Description:       a long description
### END INIT INFO

COMMAND="echo -n 'I am: '; whoami"

log () {
    echo "$@"
    logger -p user.info -t "ClueReleaseManager [$$]" "$@"
}

main () {
    case "$1" in
        stop)
        # stop your service
            echo "Stopping"
            ;;
        start)
            # run your service as user pypi
            # doesn't need password as root
            echo "Starting"
            # you probably want to start it in background
            # (don't block the other services)
            (su - pypi -c "$COMMAND") &
            ;;
        restart|force-reload)
        # restart your service
            echo "Restarting"
            ;;
        *)
        # wrong command
            echo "Unknown command: '$1'"
            ;;
    esac
}

# If you want, you can even log the whole.
# Unless you changed it it should go to /var/log/syslog
main "$1" 2>&1 | log


# Better exit with success, not sure if this can screw up Ubuntus boot process.
exit 0

update-rc.d how-to: Put it in /etc/init.d/your-script (or link to it). Make executable, and add to init services:

$ sudo chmod +x /etc/init.d/your-script
$ sudo update-rc.d your-script defaults

Now you can start and stop your service:

$ sudo your-script start
$ sudo your-script stop