How can I make this daemon/init run as a non root user?

Question

I have an init script to kick off a daemon. The problem is it runs as root. I would like it to run as a user called "deploy". Ubuntu 12.04

#! /bin/sh

# File: /etc/init.d/unicorn

### BEGIN INIT INFO
# Provides:          unicorn
# Required-Start:    $local_fs $remote_fs $network $syslog
# Required-Stop:     $local_fs $remote_fs $network $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: starts the unicorn web server
# Description:       starts unicorn
### END INIT INFO

DAEMON=/usr/local/bin/unicorn_rails
DAEMON_OPTS="-c /var/www/current/config/unicorn.rb -D"
NAME=unicorn
DESC="Unicorn"
PID=/var/www/current/shared/pid/unicorn.pid

case "$1" in
  start)
    echo -n "Starting $DESC: "
    $DAEMON $DAEMON_OPTS
    echo "$NAME."
    ;;
  *)
    echo "Usage: $NAME {start|stop|restart|reload}" >&2
    exit 1
    ;;
esac

exit 0

Answer 1

Use the start-stop-daemon utility to start your daemon. Pass the -c (or --chuid) option to run it as a different user. You'll find some examples in /etc/init.d/*.

case $1 in
  start)
    echo -n "Starting $DESC: "
    start-stop-daemon --start --chuid deploy --pidfile "$PID" --start --exec "$DAEMON" -- $DAEMON_OPTS
    echo "$NAME."
    ;;
…

Answer 2

On Ubuntu you can use just

sudo -u deploy $DAEMON $DAEMON_OPTS