Systemd Example

Let's create our own systemd service.

Our service program

• We'll use a simple bash script that endlessly outputs text into a log file:

1for (( ; ; ))
2do
3	echo "still running:" $(date)  >> /tmp/myprog.log
4	sleep 1
5done

• Save this in a file, make it executable by anyone (777) and copy to /usr/bin:

Service Definition

• Create a file called myprog.service
• Enter this text into it:

1[Unit]
2Description=myprog demo service
3
4[Service]
5User=root
6ExecStart=/bin/bash /usr/bin/myprog
7
8[Install]
9WantedBy=multi-user.target

• Copy this file to /etc/systemd/system

Activating the Service

• First, let's check if systemd knows about our service:

1sudo systemctl status myprog.service

• Let's start our service:

1systemctl start myprog.service

(requires using your password)

• Verify that the service is running now:

1sudo systemctl status myprog.service

• Validate that the log file is being written into:

1tail -f /tmp/myprog.log

• Now, let's enable it, so that it runs after the next reboot:

1systemctl enable myprog.service

(go ahead a list those symbolic links created)

• Clean everything:
  • disable the service (symlinks will be removed):

  1systemctl disable myprog.service
  

  • remove myprog.service from /etc/systemd
  • remove myprog shell script from /usr/bin:

  1sudo rm /usr/bin/myprog
  

  • Notify systemd about the change:

  1systemctl daemon-reload