Systemd

Apr 18, 2021 systemd devops

UseCase

At work, you might have executed “sudo service some-service start” and your service magically starts.

How does that happen? There are two ways I know - systemd and init.d.

Let's look at systemd.

The How to

1. Create an id-generator-service.service file that you'll provide to systemd.

   [Unit]
   Description=IDGeneratorService
      
   [Service]
   WorkingDirectory=/opt/codebase/id-generator-service
   ExecStart=/opt/codebase/id-generator-service/scripts/run.sh
   User=ubuntu
   Type=simple
   Restart=on-failure
   RestartSec=10
      
   [Install]
   WantedBy=multi-user.target
   

2. Create the run.sh file that is needed for id-generator-service.

   #!/bin/bash
      
   APP_HOME="/opt/codebase/id-generator-service"
   cd $APP_HOME
      
   OPTS=" -Xmx9046m -Xms1024m -XX:+UseG1GC -XX:+UnlockExperimentalVMOptions -XX:G1NewSizePercent=40 -XX:G1MaxNewSizePercent=75 -Djava.security.egd=file:/dev/./urandom "
   /usr/bin/java $OPTS -jar $APP_HOME/target/id-generator-service-0.0.1-SNAPSHOT.jar
   

3. Copy the service file to /etc/systemd/system to create this unit.

   ubuntu@ondemand-instance:~$ sudo cp id-generator-service.service /etc/systemd/system/
   

4. Enable this unit.

   ubuntu@ondemand-instance:~$ systemctl enable id-generator-service
   

5. It will say this unit is loaded but inactive and dead.

   ubuntu@ondemand-instance:~$ systemctl list-units --all --type=service --no-pager|grep id-generator-service
   id-generator-service.service             loaded    inactive dead    IDGeneratorService    
   

6. Start it.

   ubuntu@ondemand-instance:~$ sudo service id-generator-service start