RHCSA Systemd and Service Management Flashcards

Which systemctl command shows all unit files installed on the system, regardless of their state?

Answer: systemctl list-unit-files

`systemctl list-unit-files` lists all installed unit files and their enabled/disabled state.

A service unit has `WantedBy=multi-user.target`. What does enabling this service actually create?

Answer: A symlink in /etc/systemd/system/multi-user.target.wants/

`systemctl enable` creates a symlink in the target's `.wants/` directory under `/etc/systemd/system/`.

Which directive in a systemd service unit file prevents the service from starting until the network is fully online?

Answer: After=network-online.target Wants=network-online.target

`After=network-online.target` combined with `Wants=network-online.target` ensures the service waits for full network availability.

What is the effect of running `systemctl mask httpd`?

Answer: Creates a symlink from the unit file to /dev/null, preventing it from starting

Masking creates a symlink to `/dev/null`, making it impossible to start the service even manually.

Which command displays the dependency tree for the `sshd.service` unit?

Answer: systemctl list-dependencies sshd.service

`systemctl list-dependencies` shows all units that a given unit depends on in a tree format.

A systemd timer unit should run a job every day at 02:30. Which `OnCalendar=` value is correct?

Answer: *-*-* 02:30:00

The systemd calendar format for daily at 02:30 is `*-*-* 02:30:00` (year-month-day hour:minute:second).

Which command reloads systemd's configuration without rebooting after you add a new unit file?

Answer: systemctl daemon-reload

`systemctl daemon-reload` rescans all unit files and reloads systemd's configuration in place.