This scenario represents a classic DNS troubleshooting situation covered in the Troubleshooting
domain of the CompTIA Linux+ V8 objectives. Although the DNS zone file has been updated correctly
on the BIND server, the system continues to resolve the domain name to an outdated IP address. This
behavior strongly indicates DNS caching rather than a configuration error in the zone file itself.
Modern Linux systems that use systemd-resolved cache DNS responses locally to improve
performance and reduce external queries. Even after a DNS record is updated on the authoritative
server, cached results may persist until the cache expires or is manually cleared. The nslookup output
showing a non-authoritative answer further confirms that the response is being served from a cache
rather than directly from the updated zone data.
The correct solution is to flush the local DNS cache so the system can retrieve the updated record
from the DNS server. The command resolvectl flush-caches clears all cached DNS entries maintained
by systemd-resolved, forcing fresh queries to authoritative name servers. This aligns directly with
Linux+ V8 documentation for resolving name resolution inconsistencies caused by stale cache
entries.
The other options are incorrect for the following reasons. systemd-resolve query www.abc.com
performs a DNS lookup but does not clear cached entries. systemd-resolve status only displays
resolver configuration and statistics. service nslcd reload reloads the Name Service LDAP daemon
and is unrelated to DNS resolution or caching.
Linux+ V8 emphasizes identifying whether issues originate from services, configuration, or cached
data. In this case, flushing the DNS cache is the correct and least disruptive corrective action.
Therefore, the correct answer is D. resolvectl flush-caches.
