Which command filters the system journal for a specific service and shows entries from the last hour?

• A. journalctl -u servicename --since "1 hour ago"
• B. journalctl -u servicename --until "1 hour ago"
• C. journalctl -t servicename --since "1 hour ago"
• D. journalctl --unit servicename --since "1 hour ago"

Answer: (B)

To get logs for a specific systemd service within the last hour, you combine a unit filter with a time window. Use the service unit with a time filter that defines the start of the window, such as --since "1 hour ago". This retrieves entries from one hour ago up to now, which is exactly the last hour.

Using --until would set the end of the window to one hour ago, so you’d miss the most recent hour of logs. Filtering by a tag with -t would pull entries by a syslog tag, not specifically by the service unit, which isn’t what you want for a particular service. The long option --unit is equivalent to -u, so either form works, but the key is pairing the unit filter with --since to capture the last hour.