The questions that follow are meant to help you test your knowledge of concepts and terminology and the breadth of your knowledge. You can find the answers to these questions in Appendix A.
What is a unit?
Which command enables you to make sure that a target is no longer eligible for automatic start on system boot?
Which configuration file should you modify to apply common changes to GRUB 2?
Which command should you use to show all service units that are currently loaded?
How do you create a want for a service?
How do you switch the current operational target to the rescue.target?
Why can it happen that you get the message that a target cannot be isolated?
You want to shut down a Systemd service, but before doing that you want to know which other units have dependencies to this service. Which command would you use?
What is the name of the GRUB 2 configuration file where you apply changes to GRUB 2?
After applying changes to the GRUB 2 configuration, which command should you run?
A unit is a thing that is started by systemd. There are different types of units, such as services, mounts, sockets, and many more.
Use systemctl mask to make sure that a target is no longer eligible for automatic start on system boot.
Modify /etc/default/grub to apply common changes to GRUB 2.
systemctl --type=service shows all service units that are currently loaded.
Create a want for a service by using systemctl enable on that service.
systemctl isolate rescue.target switches the current operational target to the rescue target.
There are two types of targets: targets that can run independently and targets that cannot. Check the target unit file to find out more about this and ensure the target is isolatable (which means it can run independently).
systemctl list-dependencies --reverse shows which other units have dependencies to a systemd service.
Apply changes to GRUB 2 in /etc/default/grub.
Run grub2-mkconfig > /boot/grub2/grub.cfg after applying changes to the GRUB 2 configuration.