Running a Python Script from systemd

If you have a long-running python script (for example a discord bot) that you want running continuously, this tutorial is for you. I will show you how to create a long-running python script on any linux machine that supports systemd services.

Systemd Information

If you don't know what systemd is, this is a great overview

Below, I'll run through a very simple example of script that syncs two folders every 30 seconds

Python script

Let's go ahead and set up a virtual environment to run our folder syncing script

Virtual Env and library

Set up the virtual environment and install dirsync

python3 -m venv mcbackup
source mcbackup/bin/activate
cd mcbackup
pip install dirsync

Long running python script

Now, let's write a simple long-running script for syncing our minecraft world for backup purposes

vi sync-minecraft.py

from dirsync import sync
import time


def run():
    while True:
        # Sync our minecraft folder every 30 seconds
        sync('/opt/minecraft/server', '/opt/mccopy', 'sync')
        time.sleep(30)

if __name__ == '__main__':
    run()

Systemd

Create system service file

sudo vi /etc/systemd/system/mc-backup.service

[Unit]
Description=Sync Minecraft World
After=multi-user.target

[Service]
WorkingDirectory=/home/<username>/mcbackup
Type=simple
Restart=always
ExecStart=/home/<username>/mcbackup/bin/python /home/<username>/mcbackup/sync-minecraft.py

[Install]
WantedBy=multi-user.target

Load the service

Reload systemd to read the new service file:

sudo systemctl daemon-reload

Enable your new service:

sudo systemctl enable mc-backup.service

Start your new service:

sudo systemctl start mc-backup.service

Additional info

Now that you have the script running, you have several ways you can control the script using systemctl

Check the status:

sudo systemctl status mc-backup.service

Stop the script:

sudo systemctl stop mc-backup.service

Reload the script:

sudo systemctl restart mc-backup.service

Conclusion

There are some other things you'll probably want to do, such as log the output, maybe monitor the status of your script with healthchecks, etc... I'll cover those in future tutorials.