XK0-006 Exam Dumps - CompTIA Linux+ V8 Exam

Container management and image handling are part of modern Linux automation practices covered in CompTIA Linux+ V8. Docker images are stored in container registries such as Docker Hub, and administrators commonly need to download images to deploy containers.

The correct command for downloading an image from a Docker repository is docker image pull. This command retrieves the specified image from a configured container registry and stores it locally. When no tag is specified, Docker automatically pulls the latest available version of the image. Therefore, docker image pull debian downloads the most recent Debian image from Docker Hub.

The other options are incorrect. docker image init is not a valid Docker command and does not exist in Docker’s CLI. docker image import is used to create a Docker image from a tarball file, not to download an image from a repository. docker image save exports an existing local image into a tar archive and does not retrieve images from a remote registry.

Linux+ V8 documentation emphasizes understanding container image lifecycles, including pulling, tagging, and running images. Pulling images is a foundational step before container execution and automation workflows.

Therefore, the correct answer is B. docker image pull debian.

This scenario clearly indicates a memory exhaustion condition, which falls under the Troubleshooting domain of the CompTIA Linux+ V8 objectives. The most critical clue is the log entry stating that mysqld invoked oom-killer.

The OOM (Out-Of-Memory) killer is a Linux kernel mechanism that activates when the system runs critically low on available memory and cannot satisfy memory allocation requests. When this happens, the kernel selects a process—typically one consuming a large amount of memory—and forcibly terminates it to protect overall system stability. In this case, the MySQL daemon (mysqld) was identified as the process responsible for triggering the OOM condition.

The journalctl output explicitly confirms this behavior. Linux+ V8 documentation emphasizes that when the OOM killer is invoked, it is almost always due to physical memory exhaustion or insufficient swap space, not user intervention or application bugs alone. The additional log line showing mems_allowed=0 further supports the conclusion that the process could not allocate memory from available memory nodes.

The fact that uptime -p reports only 2 minutes of uptime strongly suggests that the system was either rebooted automatically or manually following the memory exhaustion event. Systems may reboot as part of recovery procedures after severe resource exhaustion, especially in production environments.

The other options can be ruled out. There is no indication of a user-initiated kill signal, filesystem corruption, or network connectivity issues. Network outages would not generate OOM killer messages, and filesystem errors would appear as I/O or disk-related errors in the logs.

Linux+ V8 best practices recommend addressing OOM issues by increasing system memory, tuning MySQL memory parameters, configuring swap space, or adjusting OOM scoring.

Therefore, the correct explanation is A. The process exhausted server memory.

Directory services are a key part of enterprise Linux environments and are covered under the Security domain in Linux+ V8. The Lightweight Directory Access Protocol (LDAP) is specifically designed to access and manage distributed directory information.

LDAP directories store structured, hierarchical data such as users, groups, computers, and organizational units. Linux systems commonly use LDAP for centralized authentication, authorization, and identity management. LDAP is also the foundation for services like Active Directory and FreeIPA.

The other options are incorrect. SMB is a file and printer sharing protocol. TLS is an encryption protocol used to secure communications. Kerberos (KRB-5) is an authentication protocol often used alongside LDAP but does not store directory information itself.

Linux+ V8 documentation highlights LDAP as the primary protocol for directory-based identity services. Therefore, the correct answer is C.

Kernel module management is an important part of Linux system administration and is covered in the Linux+ V8 objectives. When an administrator needs to determine metadata about a kernel module—such as its version, author, description, license, filename, and dependencies—the correct tool is modinfo.

The command modinfo bluetooth displays detailed information about the specified kernel module, including the module version if it is defined. This makes it the correct and intended command for retrieving version details of kernel modules, whether or not the module is currently loaded.

The other options are incorrect. modprobe bluetooth is used to load or unload kernel modules and does not display version information. lsmod lists loaded modules but does not show version details and does not accept module names as arguments in that manner. depmod is used to generate module dependency information and does not provide module metadata to the administrator.

Linux+ V8 documentation specifically references modinfo as the utility for inspecting kernel module properties. This command is essential for troubleshooting driver issues, verifying compatibility, and auditing kernel components.

Therefore, the correct answer is D. modinfo bluetooth.

This issue is a classic example of post-reboot connectivity troubleshooting, which falls under the Troubleshooting domain of CompTIA Linux+ V8. The administrator has correctly gathered evidence using multiple diagnostic tools, allowing the root cause to be identified through correlation.

The ss -lnt output confirms that the SSH daemon is running and listening on TCP port 22. This eliminates the possibility that the SSH service failed to start after reboot. Additionally, the uptime output shows a very low load average, indicating that system performance is not a limiting factor. The successful ping test confirms that the server is reachable at the network layer and that DNS resolution and basic connectivity are functioning correctly.

The critical clue comes from the firewall configuration. The output of firewall-cmd --list-all shows that only specific services are allowed through the firewall, such as https, dns, and cockpit. The SSH service is notably absent. On systems using firewalld, services must be explicitly allowed, even if the daemon itself is running and listening on the correct port.

As a result, incoming SSH connection attempts are being blocked by the firewall, preventing users from accessing the server remotely after reboot. This aligns precisely with option B.

The other options are incorrect. DNS is functioning, as shown by successful ping responses. System load is low and not contributing to the issue. There is no indication that users are attempting to access the web server using an incorrect protocol.

Linux+ V8 documentation emphasizes that administrators must verify both service status and firewall rules when diagnosing access issues. In this case, allowing SSH with a command such as firewall-cmd --add-service=ssh --permanent followed by a reload would resolve the problem.