Top Linux+ interview questions for 2024

With Linux continuing to expand its reach, cybersecurity professionals with Linux skills are in high demand. One way to validate your Linux chops is to earn the Linux+ certification from CompTIA. Designed for early-career IT professionals, the Linux+ exam tests your ability to install, operate, manage, secure and troubleshoot Linux environments. 

Watch the Cyber Work Podcast full-length version for more Linux+ advice from Jasmine Jackson.

What interviewers want in Linux professionals 

Linux skills are not only practical, but also in high demand in the IT and cybersecurity fields. According to the 10th Annual Linux Foundation Open Source Jobs Report, Linux skills rank first (76%) in the projects open source developers contribute to, and 58% of hiring managers have given salary increases to retain open source talent. Linux is also the most sought-after skill in cybersecurity, as it powers many of the tools and systems used by security professionals.  

Interviewers are interested in how well you grasp the fundamentals and your ability to apply this knowledge in real-world scenarios. The questions you are asked might fit into one of these categories: 

• Fundamentals: Interviewers want a deep understanding of core Linux concepts like file systems, processes, user management and basic commands. 
• Problem-solving ability: They will throw real-world scenarios your way, testing your ability to think critically and apply your knowledge. 
• Security knowledge: Expect questions assessing your knowledge of user authentication, access controls, firewalls and security tools.  
• Adaptability: Be prepared to discuss your experience with different Linux distributions, interest in emerging technologies, and commitment to continuous learning. 

Top Linux interview questions for 2024 

Now, let's explore some of the most common Linux interview questions you will likely encounter in 2024. This covers a range of fundamentals, troubleshooting scenarios, advanced topics and Linux security concepts. 

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Basic Linux concepts

1. Explain the role of the chmod command in Linux.

This question evaluates your understanding of file permissions in Linux. When preparing your answer, emphasize that the chmod command changes files and permissions, allowing or restricting access to files for users, groups and others. Highlight everyday use cases for chmod, such as granting read, write and execute permissions.

2. What are the different types of files in Linux?

Linux categorizes files by type based on their content and function. Common types include regular files that contain data. These directories serve as containers for files or other directories, symbolic links that are shortcuts to other files, block devices that represent physical hardware and character devices that represent input/output devices.  

3. Differentiate between root and sudo privileges in Linux.

Root is the superuser account with unrestricted access to the entire system. Sudo allows users to execute commands with root privileges when necessary but requires authentication and promotes security by limiting potential damage.  

4. What is the difference between a relative and absolute path in Linux?

A relative path is a path that starts from the current working directory, while an absolute path is a path that starts from the root directory. For example, if the current working directory is home/user, then a relative file path to the file.txt file in the Documents folder would be Documents/file.txt, while an absolute path would be /home/user/Documents/file.txt.  

5. What is a process in Linux, and how can you identify it?

A process is an instance of a program running on the system. Each process has a unique identifier called the process ID (PID), which can be used to manage or monitor the process. You can identify a process by using commands such as ps, top or pgrep, which display information about the processes, such as the PID, the name, the CPU and memory usage, and the status.

Intermediate-level Linux questions 

6. A developer reports that the Apache web server is not responding. How would you investigate?

The interviewer wants to test your logical troubleshooting approach for a common service issue. They want you to work through layer checks from basic to advanced. Here are some steps that you can suggest: 

Check that the Apache service is running by running this command: systemctl status httpd 

Look for errors in the logs under /var/log/httpd 

Try restarting the service and confirm firewall rules allow traffic on port 80/443 

Inspect configuration files under /etc/httpd for issues 

7. What is Logical Volume Management (LVM)?

LVM is a disk management technique that abstracts the physical layout of storage from the file system. It allows for dynamic allocation of storage space, enabling features such as resizing, volume mirroring and snapshots, providing flexibility in managing disk space.  

8. You get "Disk failure is imminent" messages in dmesg. How do you remediate?

This question gauges your ability to safely recover from outages, combining analytical skills, tools knowledge and backup verification. Here are the steps you can mention: 

Stop writing data immediately, if possible, to avoid corruption. 

Check S.M.A.R.T. data with smartctl for fail/reallocated sector counts.  

Check cable connections, but assume the disc needs replacement and plan migration to a new one.  

9. What are the different modes of Network bonding in Linux?

Network bonding in Linux can operate in several modes, including balance-tlb for transmit load balancing and balance-alb for active load balancing. These modes provide fault tolerance and load distribution between Network interfaces.  

Advanced Linux topics 

10. What is the difference between a monolithic and a microkernel in Linux?

A monolithic kernel contains all the core components and functionalities of the operating system, such as device drivers, file system, memory management and system calls. A microkernel only includes the minimal and essential components of the operating system, such as inter-process communication, scheduling and the basic hardware abstraction. The other elements and functionalities are implemented as separate processes that run in the user space.  

11. What factors might affect the boot time of two systems, one booting faster than the other?

Factors influencing boot time can include hardware differences, BIOS/UEFI settings, file system checks, and unnecessary startup scripts or services. Comparing system configurations and reviewing logs can reveal the discrepancies.  

12. When would you need to recompile a Linux kernel? Name some essential

With this question, interviewers listen for cases reflecting experience tweaking, recompiling and booting kernels rather than just memorizing build steps. 

Reasons for recompiling include enabling new hardware support, applying custom patches, optimizing performance, adding security enhancements or meeting embedded device constraints. Key steps include: 

• Configuring the build with make menuconfig 
• Executing make to compile 
• Installing modules and kernel images 
• Rebooting 
• Testing 

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Linux and cybersecurity topics 

13. How would you secure and harden a Linux server?

The interviewer wants to know if you take a layered, defense-in-depth approach with practical Linux installations rather than just conceptual answers. Your answer should include these steps: 

• Remove or disable all unnecessary services, accounts, and packages to minimize the attack surface. 

• Configure firewall rules to restrict network access and enable rate limiting. 
• Integrate authentication tools like fail2ban to prevent brute force attacks. 
• Disable root login, enforce strong user passwords and use group permissions properly. 
• Enable logging/auditing and log forwarding.
• Keep patches up to date. 

14. How would you detect crypto mining malware on Linux servers?

The interviewer wants to know your familiarity with crypto mining indicators. Here are steps to mention: 

• Monitor CPU usage spikes from tools like top and htop. 
• Check for suspicious processes and cross-reference against known hashes. 
• Review accounts and privileges for anything unusual. 
• Scan network connections for unfamiliar IPs, domains, or ports. 
• Check crontab for rogue jobs. 
• Monitor file system changes with tripwire. 
• Forward syslogs to SIEM for correlation.   

15. You discover ransomware has encrypted files on a Linux server. Outline response steps.

• Isolate the infected system immediately but preserve evidence by taking an E01 disk image for later analysis. 
• Check backups for intact files to restore service. 
• Reset credentials in case they're compromised. 
• Wipe/rebuild the infected system once recovery is done. 
• Analyze the disk image to determine the initial vector. 

Answering Linux+ interview questions 

Acing the interview is about more than having the correct answers. Here are some tips to help you effectively communicate your skills and leave a lasting impression on potential employers: 

• Ask questions to clarify expectations: Before diving into problem-solving, ask questions to ensure you fully understand the scope and expectations of the task. This will demonstrate your interest in the position and your commitment to performing well. 
• Explain your thought process: Don't just give the answer, but also explain how you arrived at it. This shows your critical thinking skills and allows the interviewer to gauge your problem-solving approach.  
• Use examples and scenarios: Use real-world examples and scenarios to illustrate your Linux skills. This will show that you have practical experience and can apply your knowledge to different situations. 
• Admit what you don't know: If you're completely stumped on a question, it's okay to say that you don't know the answer. Then, describe how you'd go about finding the answer. 

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Linux+ certification: A pathway to many careers 

Linux+ is a gateway to many career opportunities. It is the first of three certifications in CompTIA's infrastructure pathway, preparing you for various IT infrastructure roles, such as cloud, data or security. The other two certifications in the infrastructure pathway are: 

• Server+: Intermediate server administration 
• Cloud+: Cloud infrastructure management 

Linux is also essential in many cybersecurity roles, as it is the operating system of choice for many security tools and systems. Linux skills can help you perform penetration testing, forensics, malware analysis or incident response tasks. Linux+ can also be a stepping stone to CompTIA cybersecurity certifications, such as Security+, CySA+, PenTest+ or CASP+. 
 
What kind of careers can you unlock with your Linux+ certification? Here are just a few: 

• Linux engineer: Handle tasks such as system configuration, performance optimization and troubleshooting while you manage Linux-based systems. 
• System administrator: Manage and maintain IT infrastructure, including servers, networks and databases.  
• Penetration tester: Specialize in testing systems for vulnerabilities that attackers could exploit, ensuring that security measures are effective and identifying improvements. 
• DevOps engineer: Use Linux to streamline and automate software deployment processes, manage configurations and integrate continuous integration and delivery pipelines.  
• Network administrator: Manage and secure computer networks using your Linux knowledge for network infrastructure and communication protocols.   

This list merely scratches the service. With your Linux+ certification and hands-on experience, you can explore roles in data analysis, IT support, software development and more. For an idea of what you could be paid, check out our article on Linux+ salary. 

Ace your Linux interview 

Linux skills are in high demand, but you must demonstrate your abilities to stand out from other candidates. The Linux+ certification validates fundamental Linux administration skills that apply across industries. Backed by compTIA, the vendor-neutral Linux+ exam is an internationally recognized credential many employers explicitly request in job postings. 

But credentials alone won't land you the job. Nail the interview by clearly communicating examples of your hands-on Linux experience. Come prepared with stories that showcase your troubleshooting mindset, passion for learning and potential to add value. 

Here are some other tips: 

• Research the company's Linux infrastructure and cybersecurity initiatives.  
• Prepare intelligent questions that show interest in their work.  
• Follow up to reaffirm your fit or for feedback to improve next time.  

For more interview best practices, check out Infosec's free interview tips ebook and to learn more about getting your Linux+ certification, explore Infosec's Linux+ certification hub. Whether you're just starting or are ready to get certified, our certification hub will help you master the Linux tools and techniques that advance cybersecurity careers.