RHCSA Systemd and Service Management Flashcards

Which journalctl option limits output to messages from the current boot only?

Answer: -b

`journalctl -b` (or `--boot`) shows log entries from the current boot session.

A service unit's `ExecStart=` line begins with a `-` (dash) before the command path. What does this mean?

Answer: A non-zero exit code from the command is ignored

A leading `-` in `ExecStart=` tells systemd to ignore a failure (non-zero exit) of that command.

What does the `systemctl isolate rescue.target` command do?

Answer: Immediately switches the running system to rescue.target, stopping all non-essential services

`systemctl isolate` switches the active target immediately, stopping all units not required by the new target.

Where should custom drop-in configuration files for an existing systemd unit be placed?

Answer: /etc/systemd/system/.d/

Drop-in override files go in `/etc/systemd/system/.d/` as `*.conf` files so they survive package updates.

Which `systemctl` command shows the current default boot target?

Answer: systemctl get-default

`systemctl get-default` prints the symlink destination of `default.target`.

A service file has `Restart=on-failure`. Under which condition will systemd NOT restart the service?

Answer: The process exits cleanly with code 0

`Restart=on-failure` only restarts when the process exits with a non-zero code or is killed by a signal; a clean exit (code 0) is not restarted.

Which command shows journal logs for `crond.service` since yesterday in reverse chronological order?

Answer: journalctl -u crond.service --since yesterday --reverse

`journalctl -u crond.service --since yesterday --reverse` filters by unit and date, then reverses output order.