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Systemd in Linux

Varun Ladha

2 min read

·

Sep 26, 2026

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Systemd is a system and service manager for Linux operating systems. It is designed to be backwards compatible with SysV init scripts, and provides a number of features such as parallel startup of system services at boot time, on-demand activation of daemons, or dependency-based service control logic. In simple words , It provides a system and service manager that runs as PID 1 and starts the rest of the system.

Practical example to understand it

• Create app.py at /opt/systemd-learning-project/

from http.server import HTTPServer, BaseHTTPRequestHandler

class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.end_headers()
        self.wfile.write(b"Learning Systemd")

server = HTTPServer(("0.0.0.0", 8080), Handler)
server.serve_forever()

• Check it is working .
• Now create systemd file .

sudo nano /etc/systemd/system/systemd-learning-project.service

[Unit]
Description=Learning Systemd Application
After=network.target

[Service]
User=devops
WorkingDirectory=/opt/systemd-learning-project
ExecStart=/usr/bin/python3 /opt/systemd-learning-project/app.py

Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

• Create new User devops and give it access ,it is not necessary you can set your own user in User= in unit file .

sudo useradd --system --no-create-home devops
sudo chown -R devops:devops /opt/myapp/opt/systemd-learning-project

• Let the systemd know the new service

sudo systemctl daemon-reload
sudo systemctl start systemd-learning-project.service
sudo systemctl status systemd-learning-project.service

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. We can also start this with normal server boot .

sudo systemctl enable systemd-learning-project

Now let us intentionally make service crash.

• Change app.py content

import time

print("Application starting...")

time.sleep(10)

print("Application crashing!")

raise Exception("Intentional test failure")

• Let the systemd now the changes

sudo systemctl restart systemd-learning-project.service
sudo systemctl status systemd-learning-project.service

• Check logs the application is starting after every 5 second because of configuration in unit file .(Restart=on-failure
  RestartSec=5 )

sudo journalctl -u myapp -f

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• Remove that configuration and check the service restarting . The service will not restart by itself .

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Links to Learn :

• Basic Systemctl Commands : https://youtu.be/--w38cgP3kY?si=98oVIS3GjD1LkEcY