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.

Answer 1

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.

Answer 2

Yes! It is possible. :) Upstart is the way to go to make sure the service stays running. It has five packages, all installed by default:

• Upstart init daemon and initctl utility
• upstart-logd provides the logd daemon and job definition file for logd service
• upstart-compat-sysv provides job definition files for the rc tasks and the reboot, runlevel, shutdown, and telinit tools that provide compatibility with SysVinit
• startup-tasks provides job definition files for system startup tasks
• system-services provides job definition files for tty services

The learning is very enjoyable and well worth it. Upstart has a website: http://upstart.ubuntu.com/

Answer 3

3 quick suggestions...

1. Create a Start script in /etc/rc3.d (multiuser console mode) with corresponding Kill scripts in /etc/rc.0 and /etc/rc6.d to kill your Java program in a controlled way when the system powers down (runevel 0) or reboots (runlevel 6) See An introduction to Runlevels.

   You might be able to start your Java app in runlevel 2 (rc2.d) but, as a crawler, it will need TCP/IP. So make sure your networking service is available/started in your runlevel 2 beforehand. Networking is definitely up in runlevel 3.

   /etc/init.d contains all the actual start/kill scripts. /etc/rcN.d directories just contain links to them, prefixed with S or K to start or kill them respectively, per runlevel N.

2. A process run by crond should persist between logouts. Maybe add it to your crontab.

3. A process run with nohup should also persist. See nohup: run a command even after you logout.

   $ nohup java -jar myapp.jar &
   

   By default, myapp.jar's standard output will go to a file named ./nohup.out, or $HOME/nohup.out if the former isn't writeable.

Answer 4

I prefer systemd service and this is a sample for Quarkus application startup service and this is like any java application.

1. go to /etc/systemd/system

2. create Quarkus.service file

3. fill the file like this example.

    [Unit]
Description=Quarkus Application
Wants=syslog.target network.target remote-fs.target
After=remote-fs.target
Before=multi-user.target
[Service]
User=test
LimitNOFILE=102642
Environment="QUARKUS_MAILER_PASSWORD=password1"
Environment="QUARKUS_DATASOURCE_USERNAME=password2"
Environment="QUARKUS_DATASOURCE_PASSWORD=password3"
ExecStart=/usr/lib/jvm/java-11-openjdk/bin/java -jar /path/to/jar file/target/quarkus-app/quarkus-run.jar
ExecStop=/bin/kill -15 $MAINPID
Type = simple
[Install]
WantedBy=multi-user.target

4. type systemctl daemon-reload
5. systemctl enable quarkus.service
6. systemctl start quarkus.service

source

Answer 5

Also be aware when making aplications with:

  update-rc.d myscript defaults 

To have permissions 0755 and to use or get before your .sh the path. Let's say your script is on /root/test.sh , you should first change to CD /root/ before accessing test.sh.

So best way is to make a SH on init.d and there change the path to your sh and execute it in the start function.

Answer 6

Simple startup scripts with Java version checking for Linux auth-agent and Windows auth-agent.bat

Answer 7

The easiest way is to use supervisord. Please see full details at http://supervisord.org/

You can also view more details here:

Running an executable jar file when the system starts

https://www.digitalocean.com/community/tutorials/how-to-install-and-manage-supervisor-on-ubuntu-and-debian-vps