linuxexpert-practice-labs/labs/ubuntu-server/1-1-systemd-services/README.md

Ubuntu Server 1.1: Services with systemd

Stopping a service from starting, masking it, writing your own unit, and changing it with a drop-in.

Before you start

The lab doesn't install anything: installing nginx is part of task 1. It checks that nothing listens on port 8080 yet and that there's no hello.service.

Tasks

1. Install nginx, stop it from starting at boot, then make sure it can't be started at all. Undo both, so nginx is enabled and running again.
2. Write a service hello.service that runs /usr/bin/python3 -m http.server 8080 from /tmp as the user nobody, enabled at boot. curl -s localhost:8080 | head -1 prints HTML.
3. With a drop-in, make hello restart 3 seconds after it fails. After sudo kill -9 of its main PID, it's active again within a few seconds.

Hints

• systemctl disable, mask, unmask, enable --now; is-enabled, is-active.
• A unit in /etc/systemd/system/ with User=, WorkingDirectory=, ExecStart= and [Install] WantedBy=multi-user.target; systemctl daemon-reload, enable --now. ps -o user= -C python3.
• sudo systemctl edit hello, Restart=on-failure, RestartSec=3; systemctl cat hello, systemctl show hello -p MainPID.