Services and Scheduling

10 Lektionen in dieser Stufe

1. What systemd Does During Boot
   Describe units, targets and dependencies and inspect the running system. · Lab: List active units, show the dependency tree of the network target and check one service's status.
2. Writing a Service Unit for a Python Program
   Create, enable and start a unit that runs a script from a venv. · Lab: Write a unit file for the sensor logger, enable it and reboot to confirm it starts.
3. Reading Logs with journalctl
   Filter the journal by unit, time and priority. · Lab: Find yesterday's errors for one service and follow its live output.
4. Restart Policies and Start Limits
   Recover from crashes automatically without looping forever. · Lab: Make the logger crash on purpose and tune Restart, RestartSec and the start limit.
5. Dedicated Service Users and Environment Files
   Run a service with only the rights and settings it needs. · Lab: Create a system user with gpio and i2c access and move settings into an environment file.
6. Handling SIGTERM for a Clean Stop
   Catch stop signals to flush data and switch outputs off. · Lab: Add a signal handler that closes files and turns off outputs when the service stops.
7. Scheduling Jobs with cron
   Write crontab entries and avoid environment pitfalls. · Lab: Schedule an hourly CSV rotation and capture its output to a log.
8. systemd Timers as a cron Alternative
   Schedule work with calendar and monotonic timers that catch up after downtime. · Lab: Convert the cron job to a timer with Persistent=true and list its next run.
9. Rotating and Capping Logs
   Limit journal size and rotate application log files. · Lab: Set a journal size cap and write a logrotate rule for the application log.
10. Measuring and Shortening Boot Time
    Find slow units and remove what an appliance does not need. · Lab: Record systemd-analyze blame, disable two unneeded services and measure the gain.

Abschlussprojekt

A sensor-logging appliance that starts on boot under its own user, recovers from crashes, runs nightly maintenance from a timer and keeps its logs within a fixed size.

Teile für diese Stufe

• 1 × Raspberry Pi 5 or Pi 4 set from Level 1
• 1 × Sensor node hardware from Level 11

In jeder Lektion legst du die passenden Teile direkt in den Warenkorb. Raspberry Pi →