Run java jar file on a server as background process

Question

I need to run a java jar in server in order to communicate between two applications. I have written two shell scripts to run it, but once I start up that script I can't shut down / terminate the process. If I press ctrl+C or close the console, the server will shut down. Could anyone help me how to modify this script to run as a normal server?

 #!/bin/sh
java -jar /web/server.jar
echo $! 
#> startupApp.pid

Jujutsu

Answer 1

You can try this:

#!/bin/sh
nohup java -jar /web/server.jar &

The & symbol, switches the program to run in the background.

The nohup utility makes the command passed as an argument run in the background even after you log out.

Parricide

Thanks Anton,currntly im stopping the server by killing the process id.i don't think it's best practice.is thery command to to stop the server? – Jujutsu

Short answer: it depends on the server. Long answer: as far as I know, there is no safe way to shut down a process without the process supporting such graceful shut downs. For example, if it's a web server being terminated by an external signal, there is always a possibility that some requests will be lost. One way to solve this problem is to implement a graceful termination function in the server itself, e.g. by processing a special kind of requests. Then, the server can be terminated by sending it a request of that special kind. Otherwise, killing the process by its ID is the simple way. – Parricide

Using nohup should always be combined with redirecting stdout and stderr explicitly -- otherwise, you don't get control of where the logs go, and end up with an ugly nohup.out created in whichever directory this script happens to be invoked from. – Genius

@Anton when I run a script(just like your answer) with SSH EXEC runjar.sh. It started streaming the logs in my local terminal and if close my terminal my jar gets killed. How can I run a jar in the background using SSH EXEC? – Peripatetic

Answer 2

Systemd which now runs in the majority of distros

Step 1:

Find your user defined services mine was at /usr/lib/systemd/system/

Step 2:

Create a text file with your favorite text editor name it whatever_you_want.service

Step 3:

Put following Template to the file whatever_you_want.service

[Unit]
Description=webserver Daemon

[Service]
ExecStart=/usr/bin/java -jar /web/server.jar
User=user

[Install]
WantedBy=multi-user.target

Step 4:

Run your service
as super user

$ systemctl start whatever_you_want.service # starts the service
$ systemctl enable whatever_you_want.service # auto starts the service
$ systemctl disable whatever_you_want.service # stops autostart
$ systemctl stop whatever_you_want.service # stops the service
$ systemctl restart whatever_you_want.service # restarts the service

Amphibolite

This is the modern way of doing it – Odontoid

on aws ubutnu image I had to install systemd then found the image in /etc/systemd/system/ – Oscillator

Where could I find the logs with this method? – Tessin

If you have created the file, but face issue like "Failed to start ---- service", then run systemctl daemon-reload before Step 4. unix.stackexchange.com/questions/364782/… – Steakhouse

Answer 3

If you're using Ubuntu and have "Upstart" (http://upstart.ubuntu.com/) you can try this:

Create /var/init/yourservice.conf

with the following content

description "Your Java Service"  
author "You"  

start on runlevel [3]  
stop on shutdown  

expect fork  

script     
    cd /web 
    java -jar server.jar >/var/log/yourservice.log 2>&1  
    emit yourservice_running  
end script  

Now you can issue the service yourservice start and service yourservice stop commands. You can tail /var/log/yourservice.log to verify that it's working.

If you just want to run your jar from the console without it hogging the console window, you can just do:

java -jar /web/server.jar > /var/log/yourservice.log 2>&1

Formalin

Is that a systemd service? This question is not tagged linux, and very few distros have systemd by default. – Hoodlum

I will amend the question to say that this is using "upstart" which is included in ubuntu. – Formalin

I believe for the last advice if you want it to run in the background and the shell got released, you should do: java -jar /web/server.jar > /var/log/yourservice.log 2>&1 & – Czech

All system jobs by default live in the following directory: /etc/init/ ... By default, there is no /var/init/ directory in Ubuntu 14.04. – Broken

Also, starting a service requires "sudo". sudo service yourservice start – Broken

Answer 4

Run in background and add logs to log file using the following:

nohup java -jar /web/server.jar > log.log 2>&1 &

Canula