XK0-006 Exam Dumps : CompTIA Linux+ V8 Exam

This scenario represents a name resolution failure, which is a common troubleshooting case addressed in CompTIA Linux+ V8. The critical clues are the error messages returned by both curl and dig.

The curl error “Could not resolve host” indicates that the system is unable to translate the hostname into an IP address. This is confirmed by the dig output, which returns NXDOMAIN, meaning the DNS resolver cannot resolve the requested domain name. Importantly, the dig output shows that the query is reaching a DNS server (10.255.255.254), but the resolution fails, strongly pointing to a DNS client configuration issue.

Option C, reviewing and fixing the DNS client configuration file (such as /etc/resolv.conf or systemd-resolved settings), is the correct action. Linux+ V8 documentation highlights DNS misconfiguration as a primary cause of application connectivity issues. Incorrect nameserver entries, unreachable DNS servers, or misconfigured resolvers commonly produce NXDOMAIN responses.

The other options are incorrect. Firewall issues would result in connection timeouts, not DNS resolution failures. Requesting a new API endpoint is unnecessary without first confirming local DNS functionality. Internet connectivity issues would typically prevent any DNS communication, but here a DNS server is clearly being contacted.

Linux+ V8 stresses a layered troubleshooting approach: verify DNS resolution before investigating network ports or application logic. Therefore, the correct answer is C. Review and fix the DNS client configuration file.

Environment variables in Linux can exist either locally within a shell or be exported to child processes. CompTIA Linux+ V8 emphasizes the distinction between shell variables and environment variables, as this affects how applications inherit configuration values.

Option D, export ENABLE_AUTH=1, is the correct choice because it both assigns the variable and marks it for export to the environment. Once exported, the variable becomes available to all subsequently executed commands and child processes spawned from the current shell. This behavior is required when applications or scripts rely on environment variables for configuration.

Option B, ENABLE_AUTH=1, only sets a shell-local variable. While it is accessible within the current shell session, it is not inherited by child processes unless explicitly exported. Option A, let ENABLE_AUTH=1, performs arithmetic evaluation and does not export the variable. Option C incorrectly assigns the output of a command substitution and does not set the desired value.

Linux+ V8 documentation highlights export as the correct mechanism for making variables available system-wide within a user session. Therefore, the correct answer is D.

This scenario involves firewall configuration and service accessibility, which falls under the Security domain of the CompTIA Linux+ V8 objectives. The key to resolving this issue is interpreting both the firewall output and the web server status correctly.

The web server output shows that the service is actively listening on TCP port 443, which is the standard port for HTTPS (secure web traffic). The line tcp LISTEN 0 4096 *:443 *:* confirms that the web server is running properly and is ready to accept incoming connections on port 443 from any interface. This indicates that the problem is not with the web server configuration itself.

However, the firewall output clearly shows that incoming connections to port 443 are being blocked. The rules 443/tcp DENY Anywhere and 443/tcp (v6) DENY Anywhere (v6) indicate that the Uncomplicated Firewall (UFW) is explicitly denying HTTPS traffic for both IPv4 and IPv6. As a result, external clients cannot establish a secure connection to the server, even though the service is running correctly.

To resolve this issue securely and correctly, the administrator must remove the firewall rule that denies HTTPS traffic. Option C, ufw delete deny https/tcp, directly removes the blocking rule while preserving the rest of the firewall configuration. This aligns with Linux+ best practices, which emphasize making precise firewall changes rather than disabling security controls entirely.

The other options are incorrect. Option A, ufw disable, would completely turn off the firewall, creating a significant security risk. Option B, ufw allow 80/tcp, only opens HTTP traffic on port 80 and does not resolve HTTPS connectivity issues. Option D, ufw allow 4096/tcp, incorrectly attempts to open an internal socket backlog value rather than a valid service port.

Therefore, the correct and most secure solution is C.