autossh service (/etc/init.d/autossh)

autossh

#! /bin/sh
# source: https://gist.github.com/suma/8134207
# source: http://stackoverflow.com/questions/34094792/autossh-pid-is-not-equal-to-the-one-in-pidfile-when-using-start-stop-daemon

### BEGIN INIT INFO
# Provides:          autossh
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: autossh initscript
# Description:       establish a tunnelled connexion for remote access
### END INIT INFO

. /etc/environment
. /lib/init/vars.sh
. /lib/lsb/init-functions

TUNNEL_HOST=<HOST>
TUNNEL_PORT=<PORT>
TUNNEL_USER=<USER>
TUNNEL_FORWARD_PORT=<PORT>
SERVER_HOST=localhost
SERVER_PORT=22
KEY_PATH=<KEY_PATH>
MONITOR_PORT=0

NAME=autossh
DAEMON=/usr/bin/autossh
AUTOSSH_ARGS="-M $MONITOR_PORT"
SSH_ARGS="-F none -nNTv \
    -o ServerAliveInterval=30 -o ServerAliveCountMax=3 \
    -o IdentitiesOnly=yes -o ExitOnForwardFailure=yes \
    -i $KEY_PATH -R $TUNNEL_FORWARD_PORT:$SERVER_HOST:$SERVER_PORT \
    $TUNNEL_USER@$TUNNEL_HOST -p $TUNNEL_PORT"

DESC="autossh for reverse ssh"
SCRIPTNAME=/etc/init.d/$NAME
DAEMON_ARGS=" $AUTOSSH_ARGS $SSH_ARGS"

# Export PID for autossh
AUTOSSH_PIDFILE=/var/run/$NAME.pid
export AUTOSSH_PIDFILE

do_start() {
    echo "Running: $DAEMON $DAEMON_ARGS"
    start-stop-daemon --start --background --name $NAME --exec $DAEMON --test > /dev/null || return 1
    start-stop-daemon --start --background --name $NAME --exec $DAEMON -- $DAEMON_ARGS    || return 2
}

do_stop() {
    start-stop-daemon --stop --name $NAME --retry=TERM/5/KILL/9 --pidfile $AUTOSSH_PIDFILE --remove-pidfile
    RETVAL="$?"
    [ "$RETVAL" = 2 ] && return 2
    start-stop-daemon --stop --oknodo --retry=0/5/KILL/9 --exec $DAEMON
    [ "$?" = 2 ] && return 2
    return "$RETVAL"
}

case "$1" in
  start)
    log_daemon_msg "Starting $DESC" "$NAME"
    do_start
    case "$?" in
        0|1) log_end_msg 0 ;;
        2) log_end_msg 1 ;;
    esac
    ;;
  stop)
    log_daemon_msg "Stopping $DESC" "$NAME"
    do_stop
    case "$?" in
        0|1) log_end_msg 0 ;;
        2) log_end_msg 1 ;;
    esac
    ;;
  status)
    status_of_proc "$DAEMON" "$NAME" && exit 0 || exit $?
    ;;
  *)
    echo "Usage: $SCRIPTNAME {start|stop|status|restart}" >&2
    exit 3
    ;;
esac