linuxexpert-practice-labs/labs/ubuntu-server/4-2-systemd-units/README.md

Ubuntu Server 4.2: Listing systemd units

Counting and listing units by state, finding failed services, and masking.

Before you start

Like a server you don't know, this VM has a problem waiting: the lab adds a service that fails at every boot. It doesn't tell you its name. Write answers to the files in /root/lab-answers/.

Tasks

1. Count the services that are running, and write the number to /root/lab-answers/1. List the services that are installed but disabled, one per line, in /root/lab-answers/1-disabled.
2. Write a service whose ExecStart= points at a program that doesn't exist, start it, and find it the way you would on a server you don't know. You'll find the lab's failed service too: write its name and the status code systemctl status shows for it (such as 1/FAILURE) to /root/lab-answers/2. Then delete both units, run daemon-reload and reset-failed, so that systemctl --failed lists 0 loaded units.
3. Mask apport, then list every masked unit into /root/lab-answers/3. Unmask it afterwards, so systemctl is-enabled apport prints enabled again.

Hints

• systemctl list-units --type=service --state=running --no-legend, wc -l; systemctl list-unit-files --type=service --state=disabled.
• systemctl --failed, systemctl status NAME, systemctl cat NAME, journalctl -u NAME; systemctl reset-failed.
• systemctl mask, systemctl list-unit-files --state=masked, systemctl unmask.