How to create a "user service" with systemctl

Systemd is a system and service manager for Unix-like operating systems, It is responsible for starting all processes during the system boot. Systemctl is a Linux command used to control and configure systemd.

In this post, we are exploring a systemctl functionality that allows unprivileged users to run processes in the background.

Create a background task

Let's create first the task we want to run in the background, we will use this app.sh script written in Bash:

#!/bin/bash
while true ; do
    echo `date` >> /home/marco/app.log
    sleep 60
done

As you can see, it writes the date into the app.log file every 60 seconds. Put the script in your home folder and grand execute permissions:

chmod 700 app.sh

Create the systemctl user service

Systemctl will look for user service files in this path ~/.local/share/systemd/user/. Create the directory and the app.service file:

mkdir -p ~/.local/share/systemd/user/
vim ~/.local/share/systemd/user/app.service

The following configuration describes how to start the app.sh script. Do not forget to change the absolute path of the file according to your username.

[Unit]
Description= app user service

[Service]
Type=simple
WorkingDirectory=/home/marco/
ExecStart=/home/marco/app.sh
Restart=on-failure
RestartSec=5s

[Install]
WantedBy=default.target

Launch the user service

When launching a user service you have to add the --user parameter to the systemctl command:

systemctl --user start app.service

This will enable systemctl to discover the app.service in your home directory, there is no need to invoke the command with sudo.

The background task is up and running, we can check for the log output:

tail -f app.log

A new line will appear every 60 seconds.

To keep the user service running over reboot and when you log out from your server you need to enable the service:

systemctl --user enable app.service

Edit the logind.conf file:

sudo vim /etc/systemd/logind.conf

Make sure that KillUserProcesses variable is set to no:

[Login] KillUserProcesses=no

Finally, restart the logind service:

sudo systemctl restart systemd-logind

As for system services, you can check the status and stop the service:

systemctl --user status app.service
systemctl --user stop app.service

Conclusions

In this post, I have shown you how to create and run a systemctl user service. User services are convenient to run processes in the background and don't require administrative privileges.