Puma example init script. It assumes .ruby_version exist in the APP_PATH and either rbenv or rvm is used.

puma-app.sh

#!/lib/init/init-d-script

### BEGIN INIT INFO
# Provides:          my-script-name
# Required-Start:    $local_fs
# Required-Stop:     $local_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Description:       Run my app on Puma
### END INIT INFO

DESC="My app description"
NAME="my-script-name"
APP_PATH=/path/to/app
DAEMON=/bin/bash
PIDFILE=$APP_PATH/puma.pid
DAEMON_USER=app_account
[ $(id -u) = 0 ] && START_ARGS="-c $DAEMON_USER:$DAEMON_USER"

status_cmd() {
  [ -f $PIDFILE ] && kill -0 `cat $PIDFILE` 2>/dev/null
}

do_start_prepare() {
  status_cmd && exit 0
}

do_stop_prepare() {
  status_cmd || exit 0
}

do_start_cmd_override() {
  echo
  start-stop-daemon --start --quiet --pidfile $PIDFILE \
      $START_ARGS --startas $DAEMON --name $NAME --exec $DAEMON -- -l -c \
      "cd $APP_PATH && bundle exec puma -b tcp://0.0.0.0:3000 --pidfile $PIDFILE -d -e production" \
      || return 2
}

# This is required if you want service x start to exit with error if it didn't succeeded. Otherwise "FAILED" would be shown
# but the exit code would be 0 and capistrano wouldn't notice the failure for example.
# The difference from the original do_start is that we call "exit 2" in the "case 2)" condition.
do_start_override() {
  [ "$VERBOSE" != no ] && log_daemon_msg "Starting $DESC" "$NAME"
  call do_start_cmd
  case "$?" in
          0|1) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
          2) [ "$VERBOSE" != no ] && log_end_msg 1; exit 2 ;;
  esac
}

do_stop_cmd_override() {
  start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PIDFILE
}

do_status_override() {
  if status_cmd; then
    log_success_msg running
    exit 0
  else
    log_failure_msg not running
    exit 2
  fi
}

# perform a hot restart if the application is running.
# warning: sometimes the hot restart will fail and the application will exit (case the Gemfile has changed for instance).
# This is still not handled by this init script. We should probably wait a bit and see if the process is still alive and
# call start if it isn't.
do_restart_override() {
  status_cmd && kill -USR2 `cat $PIDFILE` || call do_start
}