Startup and init systems (systemd) in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is systemd in Linux?

systemd is a system and service manager for Linux. It starts and manages system services during boot and while the system runs.

beginner

What is a unit in systemd?

A unit is a configuration file that describes a service, socket, device, or other resource that systemd manages.

beginner

How do you check the status of a service named nginx using systemd?

Use the command systemctl status nginx to see if the service is running and its recent logs.

beginner

What command enables a service to start automatically at boot with systemd?

Use systemctl enable <service-name> to make a service start automatically when the system boots.

intermediate

What is the difference between systemctl start and systemctl enable?

systemctl start runs the service immediately. systemctl enable sets the service to start automatically at boot time.

Which command shows the current running services managed by systemd?

A service --status-all

B systemctl list-units --type=service

C initctl list

D chkconfig --list

systemctl list-units --type=service lists all active services managed by systemd.

What file extension do systemd unit files usually have?

A .init

B .conf

C .service

D .sh

Systemd service unit files typically end with .service.

How do you reload systemd manager configuration after editing a unit file?

A systemctl daemon-reload

B systemctl restart

C systemctl reload

D systemctl refresh

systemctl daemon-reload reloads systemd configuration to apply changes.

Which command stops a running service immediately?

A systemctl pause <service>

B systemctl disable <service>

C systemctl kill <service>

D systemctl stop <service>

systemctl stop stops the service immediately.

What does systemctl is-enabled <service> check?

A If the service is set to start at boot

B If the service is currently running

C If the service is installed

D If the service is masked

systemctl is-enabled checks if the service is enabled to start automatically at boot.

Explain how systemd manages services during system startup and how you can control them.

Think about how your computer starts apps automatically and how you can turn them on or off.

Describe the steps to create a new systemd service and make it start automatically.

Imagine setting up a new app to run when your computer boots.