Post: Using upstart with forever to manage your node.js application

service.conf.sh

#!upstart

description "your fancy description that no one will see ;)"
author "Your Name <youremail@fqdn>"

# start on every run level, 2 is the one on Ubuntu
start on runlevel [2345]

# stop on halt, maintenance or reboot
stop on runlevel [016]

# start our application with the user `user`
exec sudo -u user -i NODE_ENV=production forever start /home/user/path/to/server >> /home/user/path/to/server/syslog 2>&1

# starting log
pre-start script
  echo "[`date -u +%Y-%m-%dT%T.%3NZ`] (sys) Starting" >> /home/user/path/to/server/syslog 2>&1
end script

Why this script has .sh extension? It needs to be placed at /etc/init?