How to make a jar file run on startup & and when you log out?

Question

I have no idea where to start looking. I've been reading about daemons and didn't understand the concept.

More details :

• I've been writing a crawler which never stops and crawlers over RSS in the internet.
• The crawler has been written in java - therefore its a jar right now.
• I'm an administrator on a machine that has Ubuntu 11.04 .
• There is some chances for the machine to crash , so I'd like the crawler to run every time you startup the machine.
• Furthermore, I'd like it to keep running even when i logged out. I'm not sure this is possible, but most of the time I'm logged out, and I still want to it crawl.

Any ideas? Can someone point me in the right direction?

Just looking for the simplest solution.

Solution

Here's a easy way to do that using SysVInit. Instructions:

1. Create the start and the stop script of your application. Put it on some directory, in our example is:

   • Start Script: /usr/local/bin/myapp-start.sh
   • Stop Script: /usr/local/bin/myapp-stop.sh

   Each one will provide the instructions to run/stop the app. For instance the myapp-start.sh content can be as simple as the following:

   #!/bin/bash
   
   java -jar myapp.jar 
   

   For the stop script it can be something like this:

   #!/bin/bash
   # Grabs and kill a process from the pidlist that has the word myapp
   
   pid=`ps aux | grep myapp | awk '{print $2}'`
   kill -9 $pid
   

2. Create the following script (myscript) and put it on /etc/init.d.

   /etc/init.d/myscript content:

   #!/bin/bash
   # MyApp
   #
   # description: bla bla
   
   case $1 in
       start)
           /bin/bash /usr/local/bin/myapp-start.sh
       ;;
       stop)
           /bin/bash /usr/local/bin/myapp-stop.sh
       ;;
       restart)
           /bin/bash /usr/local/bin/myapp-stop.sh
           /bin/bash /usr/local/bin/myapp-start.sh
       ;;
   esac
   exit 0
   

3. Put the script to start with the system (using SysV). Just run the following command (as root):

   update-rc.d myscript defaults 
   

PS: I know that Upstart is great and bla bla, but I preffer the old SysV init system.

Comments

[Admin]

And when i logout , will it still run on background?

[John John Pichler]

But how do the system will know what parameter will use? How to set to be the "start". Tried here and it did not work.

[Tobia]

This works, but the command "service myapp start" do not exit the command.

[Codevalley]

Now how to use the start|stop|restart options in myscript ?

[Codevalley]

Also, even after doing the 3 steps, my jar is not running on startup. Are you sure if we have to change permissions, or path or something like that?

[Matt Schuetze]

@Codevalley, as I mentioned, this method is for the SysV init. To use service or other command you'll need to write a upstart job. But if you are going to do this, you should write a systemd one (since it is becoming the standard)

[er-han]

This worked for me, thank you. But I had to make the last script ('myscipt' in your example) executable with this command: chmod 755 /etc/init.d/myscript . Otherwise update-rc.d command couldn't execute it.

[Jared Chu]

save my day, I just forgot to chkconfig myscript on

[Admin]

From the Upstart website, as of 2019: "Project is in maintaince mode only. No new features are being developed and the general advice would be to move over to another minimal init system or systemd"

[Vlad]

I have update-rc.d: error: myscript Default-Start contains no runlevels, aborting. So it also requires some headings like here