Restart a crashed process (python) script automatically in linux

Question

I want to restart a process (python script) automatically if it ends/crashed. Below my bash init.d script so far. I was thinking to replace the do_start() call in the start section with:

until do_start; do
   echo "Restarting.." >> error.txt
   sleep 1
done

Unfortunately this seems not to be working. My script is not restarting. Has anyone a tip?

#!/bin/bash

### BEGIN INIT INFO
# Provides:          RPiQuadroServer
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Put a short description of the service here
# Description:       Put a long description of the service here
### END INIT INFO

WORK_DIR="/var/lib/RPiQuadroServer"
DAEMON="/usr/bin/python"
ARGS="/usr/local/bin/RPiQuadroServer.py"
PIDFILE="/var/run/RPiQuadroServer.pid"
USER="root"

. /lib/lsb/init-functions

do_start() {
  log_daemon_msg "Starting system $DAEMON $ARGS daemon"
  mkdir -p "$WORK_DIR"
  /sbin/start-stop-daemon --start --pidfile $PIDFILE \
    --user $USER --group $USER \
    -b --make-pidfile \
    --chuid $USER \
    --exec $DAEMON $ARGS
  log_end_msg $?
}

do_stop() {
  log_daemon_msg "Stopping system $DAEMON $ARGS daemon"
  /sbin/start-stop-daemon --stop --pidfile $PIDFILE --verbose
  log_end_msg $?
}

case "$1" in
  start)
    do_start
    ;;
  stop)
    log_daemon_msg "Stopping system $DAEMON $ARGS daemon"
    do_stop
    ;;
  restart|reload|force-reload)
    do_stop
    do_start
    ;;
  status)
    status_of_proc "$DAEMON $ARGS" "$DAEMON $ARGS" && exit 0 || exit $?
    ;;
  *)
    echo "Usage: /etc/init.d/$USER {start|stop|restart|status}"
    exit 1
    ;;
esac

Answer 1

You need to have some kind of a supervision . For example monit . It will do what you described: start/restart process:

For example:

check process RPiQuadroServe pidfile /var/run/RPiQuadroServer.pid                      
 start program = "/etc/init.d/RPiQuadroServe start"                               
 stop program = "/etc/init.d/RPiQuadroServec stop"                                 

Answer 2

In the until loop, the loop executes until the do_start command executes successfully, which means it continues as long as do_start exits with any exit code other than 0 . But in your code, you didn't set any exit status, so it would be 0 . You might want to set the exit code by for example return $? after executing Python code.