monitor bash script execution using monit

Question

We have just started using monit for process monitor and pretty much new in monit. I have a bash script at /home/ubuntu/launch_example.sh. This is continuously running. is it possible to monitor this using monit? monit should start the script if it bash scripts terminates. What should be syntax.I tried below syntax but all the commands are not being executed as ubuntu user, like shell script calls some python scripts.

check process launch_example
matching "launch_example"
start program = "/bin/bash -c '/home/ubuntu/launch_example.sh'"
as uid ubuntu and gid ubuntu
stop program = "/bin/bash -c '/home/ubuntu/launch_example.sh'"
as uid ubuntu and gid ubuntu

boppy boppy · Accepted Answer · 2021-02-08T18:49:09

The simple answer is "no". Monit is just for monitoring and is not some kind of supervisor/process manager. So if you want to monitor your long running executable, you have to wrap it.

check process launch_example with pidfile /run/launch.pid
  start program = "/bin/bash -c 'nohup /home/ubuntu/launch_example.sh &'"
    as uid ubuntu and gid ubuntu
  stop program = "/bin/bash -c 'kill $(cat /run/launch.pid)'"
    as uid ubuntu and gid ubuntu

This quick'n'dirty way also needs an additional line for your launch_example.sh to write the pidfile (pidfile matching should always be preferred over string matching) - it could be just the first line after she shebang. It simply writes the current process ID to the pidfile. Nothing fancy here ;)

echo $$ > /run/launch.pid

In fact, it's not even hard to convert your script into a systemd unit. Here is an example on how to. User binding, restarts, pidfile, and "start-on-boot" can then be managed through systemd (eg. start program = "/usr/bin/systemctl start my_unit").

monitor bash script execution using monit

1 Answers