systemctl mask (creates /etc/systemd/system/ .service → /dev/null symlink)

Question 1

What command shows all currently running services/processes?

Accepted Answer

ps aux (shows all processes with details) or systemctl list-units --type=service (shows systemd services)

Question 2

How do you start, stop, or restart a service in systemd?

Accepted Answer

systemctl start/stop/restart <service-name> (requires sudo for most services)

Question 3

What command enables a service to auto-start on boot?

Accepted Answer

systemctl enable <service-name> (creates symlink in /etc/systemd/system/)

Question 4

How do you check if a service is running and its status?

Accepted Answer

systemctl status <service-name> (shows enabled/active state and recent logs)

Question 5

What's the difference between 'systemctl restart' and 'systemctl reload'?

Accepted Answer

restart: stops then starts service (breaks connections). reload: reloads config without stopping (graceful, if supported)

Question 6

How do you view real-time service logs?

Accepted Answer

journalctl -u <service-name> -f (follows log output; -n 50 shows last 50 lines)

Question 7

What pattern checks if a service failed and shows why?

Accepted Answer

systemctl status then journalctl -u -e for detailed error context

Question 8

How do you find which service is listening on a specific port?

Accepted Answer

sudo lsof -i : or sudo netstat -tlnp | grep (netstat deprecated, use ss -tlnp)

Question 9

What command gracefully reloads all systemd configuration without restarting services?

Accepted Answer

systemctl daemon-reload (required after editing .service files in /etc/systemd/system/)

Question 10

How do you mask (disable) a service so it cannot be started even manually?

Accepted Answer

systemctl mask (creates /etc/systemd/system/.service → /dev/null symlink)

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