The CompTIA Linux+ (XK0-005) validates skills in Linux system administration including managing systems, securing Linux environments, scripting and automation, and troubleshooting. It is vendor-neutral and covers all major distributions including Ubuntu, Red Hat, CentOS, and SUSE. Download the official CompTIA Linux+ Exam Objectives for the full domain breakdown.
Linux+ Practice Quiz
1. The security team flagged q1-budget.xlsx during an audit because the current mode allows any authenticated user to modify it. Compliance requires the file owner (cfo) to read and write, members of the finance group to read only, and all other users to have no access whatsoever. Which chmod command brings the file into compliance?
Right answer (B): That's correct! 640 gives owner read+write (6), group read-only (4), and others no access (0), exactly matching the requirement.
Wrong answers:
- A): 764 grants the group read, write, and execute, which exceeds the stated requirement.
- C): 755 grants read and execute to both group and others, violating the no-access-for-others rule.
- D): 600 restricts access to the owner only and does not give the group the required read access.
2. After deploying a fresh RHEL 9 web server, the administrator confirms that httpd is currently disabled and inactive as shown below. The change window is short and the service must come up immediately and survive the next reboot without a second command. Which single systemctl invocation accomplishes both goals?
Right answer (C): That's correct! systemctl enable --now both enables the service at boot and starts it immediately in a single operation.
Wrong answers:
- A): systemctl start alone runs the service immediately but does not configure it to start automatically on reboot.
- B): systemctl enable alone creates the boot symlink but does not start the service in the current session.
- D): systemctl restart only stops and restarts a running service and has no effect on boot-time behavior.
3. The /data filesystem on db01 is at 96% capacity as shown below, and an outage cannot be tolerated, so unmounting is not an option. Plenty of free PE remain in vg01. Which sequence correctly grows lv_data by 10 GB and makes the new space immediately usable in the live ext4 filesystem?
Right answer (A): That's correct! Extend the logical volume with lvextend first, then grow the filesystem with resize2fs to use the new space.
Wrong answers:
- B): Resizing the filesystem before extending the LV would attempt to grow beyond the volume boundary and fail or cause corruption.
- C): vgextend adds physical volumes to a volume group and is not used to extend logical volumes.
- D): pvcreate initializes physical volumes for LVM and cannot resize an existing logical volume.
4. Nginx is running and bound to ports 80 and 443 as shown below, but external clients receive connection refused errors because firewalld is blocking the traffic. The administrator needs the rules to survive a reboot and take effect without restarting the service. Which command set correctly opens HTTP and HTTPS in the public zone?
Right answer (D): That's correct! The --permanent flag writes the rule to persistent config and --reload applies it to the running firewall, allowing both HTTP and HTTPS.
Wrong answers:
- A): iptables uses the legacy framework and does not integrate with firewalld's zone-based management.
- B): Without --permanent, the rule is only in runtime configuration and is lost after a reboot.
- C): ufw is specific to Ubuntu and Debian-based systems, not Red Hat systems running firewalld.
5. Apache cannot write user uploads even though DAC ownership and mode look correct, and SELinux is enforcing with a default_t label on the directory as shown below. Before changing any contexts or permissions, the administrator wants to confirm exactly which AVC denial is firing and what target type SELinux expects. Which command should be run FIRST to diagnose the issue?
Right answer (B): That's correct! ausearch -m avc queries the audit log for AVC denial messages, showing exactly what SELinux is blocking and why.
Wrong answers:
- A): setenforce 0 disables enforcement, masking the problem instead of diagnosing it and creating a security risk.
- C): chmod 777 changes DAC permissions but does not resolve SELinux context mismatches.
- D): chown adjusts ownership at the DAC layer, but SELinux operates independently through MAC labels.
6. The backup engineer is filling in the missing fields shown below for a new cron entry that must execute /opt/scripts/backup.sh every day at exactly 2:30 AM local time. Cron's five time fields read minute, hour, day-of-month, month, and day-of-week from left to right. Which entry correctly schedules the job?
Right answer (C): That's correct! The crontab format is minute, hour, day-of-month, month, day-of-week, so 30 2 * * * runs at 2:30 AM every day.
Wrong answers:
- A): 2 30 * * * reverses the minute and hour fields, producing minute 2 of hour 30, which is invalid.
- B): Placing 2 and 30 in the day-of-month and month fields gives entirely different scheduling semantics.
- D): 0 2 30 * * runs at 2:00 AM only on the 30th of each month, not daily at 2:30 AM.
7. The script shown below must create /opt/backups only when that directory does not already exist. If the path already exists as a directory the script should skip mkdir to avoid the "File exists" error and the resulting non-zero exit caused by `set -e`. Which conditional belongs in place of __CONDITIONAL__?
Right answer (A): That's correct! The -d flag tests for a directory and the ! operator negates the test so mkdir only runs when the directory does not exist.
Wrong answers:
- B): -f tests for a regular file, not a directory, so it would not correctly detect an existing directory at that path.
- C): -e checks if any file exists, and the logic is inverted, trying to create the directory when it already exists.
- D): -d without negation runs mkdir when the directory already exists, causing an error.
8. The root filesystem on app01 is at 99% capacity as shown below, and applications are starting to fail when they try to write logs and PID files. df has confirmed which mount is full but does not say WHERE the space went inside that filesystem. Which command identifies the ten largest top-level directories under / sorted from biggest to smallest?
Right answer (B): That's correct! du -sh /* summarizes directory sizes, and piping through sort -rh | head -10 reveals the ten largest space consumers.
Wrong answers:
- A): df -h shows filesystem-level usage totals but does not break down which directories or files use the space.
- C): free -m displays memory and swap usage, not disk space utilization.
- D): top -bn1 shows running processes and CPU or memory usage, which is unrelated to disk consumption.
9. The user-facing web application returns connection refused even though systemd reports httpd as active and the NIC has a valid IP as shown below. SSH to the host works fine, ruling out a full network outage. Which command should be run FIRST to confirm whether httpd is actually bound to TCP port 80 and which PID owns the socket?
Right answer (C): That's correct! ss -tlnp lists listening TCP sockets with process names, and grepping :80 confirms whether the web server is actively listening.
Wrong answers:
- A): ping localhost only verifies the loopback interface is up and says nothing about which services are listening.
- B): traceroute tests the network path to a remote host and does not verify local service availability.
- D): nslookup tests DNS resolution, which is unrelated to whether a local service process is listening.
10. Load average on app07 has climbed above 40 with multiple processes stuck in uninterruptible sleep (D state) as shown below, which typically points at the kernel waiting on hardware or I/O. Before tuning the database or rebooting, the administrator wants to look at the central log that captures kernel ring messages, disk errors, and OOM events. Which log file should be checked FIRST?
Right answer (D): That's correct! /var/log/syslog (Debian/Ubuntu) or /var/log/messages (RHEL/CentOS) is the primary system log capturing kernel messages, service errors, and hardware events that commonly drive high load.
Wrong answers:
- A): auth.log records authentication events like logins and sudo usage, which rarely cause high load averages.
- B): mail.log captures email server activity and is only relevant if the mail subsystem is the suspected cause.
- C): cron logs scheduled task execution and is only relevant if a specific cron job is suspected of causing the spike.
Quiz Complete!
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Free Linux+ Flashcards
What is the difference between hard links and symbolic links in Linux?
Click to flipHard links share the same inode and data blocks, so they persist even if the original file is deleted. Symbolic links point to a file path and break if the target is moved or deleted.
Frequently Asked Questions
The Linux+ (XK0-005) passing score is 720 on a 100-900 scale. The exam includes up to 90 questions with a 90-minute time limit.
Linux+ is valuable for IT professionals working with Linux servers, cloud infrastructure, or DevOps pipelines. It is DoD 8140 approved and validates practical Linux system administration skills across all major distributions.
Linux+ is vendor-neutral covering all major distributions, while RHCSA is Red Hat-specific. Linux+ is multiple-choice with PBQs, while RHCSA is entirely performance-based on a live system. Many professionals hold both certifications.
CompTIA recommends at least 12 months of hands-on Linux administration experience. Familiarity with the command line, package management, and basic networking is strongly recommended before attempting the exam.
The Linux+ exam voucher costs approximately $369 USD. CompTIA offers bundles with retake vouchers and study materials at a discounted rate.
Yes, Linux+ includes performance-based questions that simulate real scenarios like configuring services, writing shell scripts, managing file permissions, or troubleshooting network connectivity.
Linux+ is valid for three years. Renewal requires 50 CEUs through CompTIA's Continuing Education program or passing a higher-level CompTIA certification exam.
Linux+ qualifies you for Linux administrator, systems engineer, DevOps engineer, cloud engineer, and site reliability engineer roles. Salaries typically range from $70,000 to $105,000 depending on experience and location.
Practice with both Debian-based (Ubuntu) and Red Hat-based (CentOS, Rocky Linux, Fedora) distributions. The exam tests concepts across distribution families, including differences in package management and init systems.
Yes, the XK0-005 exam covers container fundamentals including Docker and Podman, orchestration basics, cloud-init, and infrastructure as code concepts as they relate to Linux environments.
Linux+ and LPIC-1 cover similar topics, but Linux+ is more recognized in North America and is DoD approved. LPIC-1 has stronger international recognition. Choose based on your geographic job market and employer preferences.
CertLabz offers full-length Linux+ practice exams with 90+ questions, virtual Linux labs, PBQ simulations, domain breakdowns with progress tracking, and flashcards. Plans start at $10/month.