What do the UNIT, LOAD, and ACTIVE columns mean?

Great question! Understanding these columns is key to interpreting the output of systemctl. Let's break them down:

• UNIT: This simply refers to the name of the service unit. In the context of systemd, everything is managed as a "unit." For services, these names typically end with .service, like atd.service or auditd.service. It tells you what service is being listed.

• LOAD: This column indicates whether the systemd daemon has successfully parsed the unit's configuration file and loaded it into memory.

  • If you see loaded, it means systemd understood the service's definition and has it ready.
  • Other states like not-found or error would indicate issues with the unit file itself.

• ACTIVE: This is the high-level activation state of the unit. It tells you whether the service is generally running or not.

  • active usually means the service successfully started and is operating as expected.
  • inactive means the service is not currently running.
  • failed means the service attempted to start but encountered an error.

Think of it this way:

• UNIT is what service it is.
• LOAD is if systemd knows about it.
• ACTIVE is if it's currently running successfully.

Do these explanations make sense? Feel free to ask if you want to dive deeper into any of them, or if you're ready to proceed to the next parts of the step!