Free Practice Questions for CompTIA XK0-006 Exam

DNS client configuration is a foundational Linux networking task covered in Linux+ V8 system management objectives. When an administrator needs to specify the IP address of a DNS server that the system should use for name resolution, the correct file to modify is /etc/resolv.conf.

The /etc/resolv.conf file defines DNS resolver settings, including one or more nameserver entries that specify the IP addresses of DNS servers. Applications and system services rely on this file to resolve hostnames to IP addresses.

The other options are incorrect. /etc/whois.conf configures WHOIS queries. /etc/nsswitch.conf controls the order of name resolution sources but does not define DNS server IP addresses. /etc/dnsmasq.conf configures a local DNS caching service, not the system-wide resolver directly.

Linux+ V8 documentation highlights /etc/resolv.conf as the authoritative DNS client configuration file, though it may be dynamically managed by tools such as NetworkManager or systemd-resolved.

Therefore, the correct answer is B. /etc/resolv.conf.

Package management troubleshooting is a critical Linux administration skill addressed in CompTIA Linux+ V8. After system patching, identifying which packages were installed, updated, or removed is often the first step in diagnosing application failures.

The dnf history command is specifically designed for this purpose. It displays a chronological list of all DNF transactions, including installations, upgrades, downgrades, and removals. Each transaction is assigned an ID and includes timestamps, affected packages, and actions taken. This allows administrators to correlate application failures with recent changes.

Option A is correct because it provides historical context rather than just current package state. Linux+ V8 documentation highlights dnf history as an essential auditing and rollback tool.

The other options are insufficient. dnf list shows installed or available packages but does not indicate when they were installed. dnf info displays metadata for a specific package but does not show transaction history. dnf search is used to find packages by name or description.

By reviewing recent transactions with dnf history, administrators can quickly identify problematic updates and take corrective action, such as rolling back a package.

Therefore, the correct answer is A.

Version control rollback operations are a core DevOps skill covered in the Linux+ V8 objectives. When changes in a local Git repository break an application and must be reverted, the administrator must choose a command that directly undoes those changes.

The command git reset is the most appropriate option in this scenario. It allows the engineer to move the current branch pointer (HEAD) to a previous commit, effectively discarding or undoing local changes. Depending on the reset mode (--soft, --mixed, or --hard), the engineer can control whether changes are preserved in the staging area or working directory. This flexibility makes git reset the primary tool for reverting problematic local changes.

The other options are not suitable. git pull fetches and merges changes from a remote repository and does not revert local modifications. git rebase rewrites commit history and is used to reapply commits on top of another base, not to undo broken changes. git stash temporarily saves uncommitted changes for later use but does not revert the repository to a stable state.

Linux+ V8 documentation emphasizes that git reset is commonly used during local development when changes need to be undone quickly before being shared with others. Therefore, the correct answer is B.

Version control is a core DevOps practice, and CompTIA Linux+ V8 includes Git fundamentals as part of automation and orchestration objectives. To create a new local Git repository, the correct command is git init.

The git init command initializes a new Git repository in the current directory by creating a hidden .git directory. This directory contains all the metadata required for version control, including commit history, branches, configuration settings, and object storage. After running git init, the directory becomes a fully functional local repository ready to track files and commits.

The other options do not create a new repository. git clone is used to copy an existing remote repository to a local system, not to create a new one. git config is used to set Git configuration values such as username, email, or default editor. git add stages files for commit but only works after a repository has already been initialized.

Linux+ V8 documentation highlights git init as the foundational command for starting version control in new projects. This command is frequently used in DevOps workflows when creating infrastructure-as-code repositories, automation scripts, or application source trees from scratch.

By initializing a local repository, engineers can begin tracking changes, collaborating with others, and integrating Git into CI/CD pipelines. Therefore, the correct answer is A. git init.

Password policy enforcement is a critical component of system security covered in the CompTIA Linux+ V8 objectives. One common control implemented in Linux systems is restricting how frequently users can change their passwords, often referred to as minimum password age enforcement.

The primary reason multiple password changes within a short time frame are not allowed is to prevent password cycling attacks. Without this restriction, a user could repeatedly change their password in quick succession to bypass password history controls and eventually reuse a previously compromised or weak password. Option C accurately describes this scenario and aligns directly with Linux+ V8 security guidance.

Linux systems enforce this behavior through tools such as chage and PAM (Pluggable Authentication Modules). Administrators can configure minimum password age values to ensure users must wait a defined period before changing passwords again. This ensures that password history requirements are effective and meaningful.

The other options are incorrect. Option A confuses password expiration with brute-force mitigation, which is typically addressed through account lockout policies. Option B refers to password complexity, which is enforced through character requirements rather than change frequency. Option D is unrelated, as password expiration policies do not enforce multifactor authentication.

Linux+ V8 documentation emphasizes layered access controls, and preventing password reuse through enforced timing restrictions is a core principle of secure authentication design.

Therefore, the correct answer is C.

Comprehensive and Detailed Explanation From Exact Extract:

To add an existing user (myuser) to an existing group (finance) without removing them from other groups, the correct command is usermod -aG finance myuser. The -aG option appends the user to the supplementary group(s) specified.

Other options:

A. groupadd is for creating new groups, not adding users to groups.

B. groupmod is for modifying group properties, not user membership.

C. useradd creates new users; not applicable to existing users.

Comprehensive and Detailed 250 to 350 words of Explanation From Linux+ V8 documents:

Password complexity is a fundamental concept within the Security domain of CompTIA Linux+ V8. Complex passwords significantly reduce the risk of successful brute-force, dictionary, and credential-stuffing attacks. Linux+ emphasizes evaluating passwords based on length, character variety, unpredictability, and resistance to common word patterns.

Option C, H3s@1dSh3t0|d, is the most complex password among the choices. It demonstrates strong security characteristics by incorporating:

Uppercase letters (H, S)

Lowercase letters (s, d, t)

Numbers (3, 1, 0)

Multiple special characters (@, |)

A longer overall length compared to some other options

Additionally, option C uses character substitution (leet-style) in a way that breaks up recognizable words more effectively than the other choices. This significantly increases entropy and makes the password harder to guess using rule-based or hybrid cracking techniques.

Option A includes uppercase letters and numbers but lacks special characters and is relatively short. Option B includes special characters and mixed case, but it still closely resembles readable words, making it more susceptible to dictionary-based attacks. Option D uses only alphabetic characters and clear word patterns, making it the weakest choice.

Linux+ V8 documentation highlights that the strongest passwords combine length with diverse character classes and minimal predictability. Password C best meets all of these criteria and would score highest against common password-cracking strategies.

Therefore, the correct answer is C. H3s@1dSh3t0|d.

Log monitoring is a common troubleshooting task in Linux system administration, and Linux+ V8 covers command-line tools for real-time log analysis. The requirement in this scenario is twofold: view log entries as they occur and simultaneously save them to another file.

The command tail -f /var/log/apache2/error.log | tee logfile.txt fulfills both requirements. The tail -f command follows the log file in real time, displaying new entries as they are written. The pipe (|) sends this output to the tee command, which writes the data to logfile.txt while also displaying it on standard output.

The other options are insufficient. Option A redirects output to a file but prevents real-time viewing. Option C appends output but still suppresses terminal display. Option B is syntactically invalid and does not use a proper command for writing output.

Linux+ V8 documentation specifically references tee as a useful utility for duplicating command output streams. This makes option D the correct and most effective solution.

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.

Password management is a core topic in the Security domain of CompTIA Linux+ V8. Password expiry policies are implemented to reduce the risk associated with long-lived credentials.

The primary reason for enforcing password expiration is to mitigate the risk of exposed or compromised passwords. If a password is leaked through phishing, malware, keylogging, or data breaches, limiting its lifespan reduces the window of opportunity for attackers to exploit it. Requiring periodic password changes ensures that compromised credentials eventually become invalid.

Option B correctly captures this security objective. Linux+ V8 documentation emphasizes minimizing credential exposure as a key principle of access control.

The other options are secondary or incorrect. Avoiding password reuse and increasing complexity are addressed through password history and complexity policies, not expiration alone. Password expiry does not force passwordless authentication, making option C incorrect.

Therefore, the correct answer is B. To mitigate the use of exposed passwords.