systemctl start/stop service: How to Setup Upstart Script and Respawn Process in Ubuntu, CentOS, Redhat Linux

Linux systemd upstart - upstart script

How to write startup script for systemd?

systemd is the latest service management utility in all latest version of Linux distribution such as Ubuntu OS, Redhat OS, CentOS.

That’s why Ubuntu 17.4 and Redhat 7.4 version now supports systemctl command as an upstart script. If you are on older version of Linux OS then you may need to look at bottom of this page to see older init.d script

We are going to discuss below things in this tutorial

Setting up systemd service unit
How to configure systemd?
How to enable it systemd?
How start process automatically using systemd?
How to stop and respawn process using systemd?

Setup Steps for this tutorial:

Prerequisite: We have compiled version of CrunchifyAlwaysRunningProgram.java program at /tmp/crunchify folder. This java process will keep running in background forever. You could download program from here.

Once you download it then try to compile it and run it to make sure it’s working.

root@crunchify:/tmp/crunchify# ls -ltr
-rw-r--r-- 1 root root  120 Oct  6 17:57 crunchify.tar.gz
drwxr-xr-x 2 root root 4096 Oct  6 18:01 tomcat
drwxr-xr-x 2 root root 4096 Oct  6 18:02 java
-rw-r--r-- 1 root root  621 Oct  7 16:06 package
-rwxrwxrwx 1 root root  838 Oct  7 16:07 CrunchifyAlwaysRunningProgram.java
-rwxrwxrwx 1 root root 1295 Oct  8 14:38 CrunchifyAlwaysRunningProgram.class

root@crunchify:/tmp/crunchify# javac CrunchifyAlwaysRunningProgram.java

root@crunchify:/tmp/crunchify# java CrunchifyAlwaysRunningProgram 
always running program ==> Sun Oct 08 14:39:14 UTC 2017
always running program ==> Sun Oct 08 14:39:16 UTC 2017
...
...
...

You can type CTRL + C to quit program.

Now let’s get started on setting up systemd auto startup script for above program.

Step-1

Go to folder /lib/systemd/system
Type cd /lib/systemd/system

Step-2

create file crunchify.service (change filename accordingly)
put below content into it

[Unit]
Description=Crunchify Java Process Restart Upstart Script
After=auditd.service systemd-user-sessions.service time-sync.target

[Service]
User=root
TimeoutStartSec=0
Type=simple
KillMode=process
export JAVA_HOME=/opt/java/jdk-9
export PATH=$PATH:$JAVA_HOME/bin
WorkingDirectory=/tmp/crunchify
ExecStart=/opt/java/jdk-9/bin/java -cp /tmp/crunchify CrunchifyAlwaysRunningProgram
Restart=always
RestartSec=2
LimitNOFILE=5555

[Install]
WantedBy=multi-user.target

Step-3

Save file
Provide execute permission using chmod 755 crunchify.service

Step-4

Load crunchify.service using command systemctl daemon-reload
Enable crunchify.service using command systemctl enable crunchify.service
Start crunchify.service using command systemctl start crunchify
Check status of crunchify.service using command systemctl status crunchify

Step-5

Now check if process is running or not??
Type command ps -few | grep java to see all running Java processes
You should see something like this

root@crunchify:/lib/systemd/system# ps -few | grep java
root     28631     1  0 14:02 ?        00:00:03 /opt/java/jdk-9/bin/java -cp /tmp/crunchify CrunchifyAlwaysRunningProgram
root     28853 28226  0 14:46 pts/0    00:00:00 grep java

That means process 28631 is starting using your upstart script. You may have different process ID.

How to verify if your systemd crunchify.service is working or not?

Try to kill process using kill -9 28631 and you should see new process should be created automatically.
In my case new process ID 28887 created

root@crunchify:/lib/systemd/system# kill -9 28631
root@crunchify:/lib/systemd/system# ps -few | grep java
root     28887     1 17 14:48 ?        00:00:00 /opt/java/jdk-9/bin/java -cp /tmp/crunchify CrunchifyAlwaysRunningProgram
root     28900 28226  0 14:48 pts/0    00:00:00 grep java

Video: Complete Live systemd upstart script setup example:

This video contains – How to Setup systemd startup/upstart script in CentOS, Redhat, Ubuntu Linux OS?

How to automatically execute shell script at startup boot
How To Create a systemd Service in Linux (CentOS 7)
How To Configure a Linux Service to Start automatically?
Centos 7 systemd startup script
Ubuntu systemd startup script

Want to learn more on systemd? Here is a cheat sheet for your reference.

Linux Systemd Command CheatSheet

I hope you learn everything about systemd command and setting up upstart script on all types of Linux OS.

STOP: For Older Version of OS ONLY

If you are running older version of Redhat, Ubuntu, CentOS version then you will need to have script in this format.

Go to /etc/init
Create file crunchify.conf

# Run Crunchify's Java program indefinitely
#

description     "Crunchify Java Process Restart Upstart Script"
author "Crunchify.com (App Shah)"

start on runlevel [2345]
stop on runlevel [!2345]

respawn
respawn limit 10 5

script
    su - root << 'EOF'
    export JAVA_HOME=/opt/java/jdk-9
    export PATH=$PATH:$JAVA_HOME/bin
    exec /opt/java/jdk-9/bin/java -cp /tmp/crunchify CrunchifyAlwaysRunningProgram
    EOF
end script