Top 70+ Linux Interview Questions and Answers

6.6K

Linux is an operating system, just like Windows or macOS. It was created in 1991 by a man named Linus Torvalds. He built it as a free and open system so anyone could freely use it or modify it. Linux is based on another system called UNIX, and today, it has become the backbone of servers, cloud platforms, and even smartphones. Because it is used in so many places, Linux skills are in high demand across tech roles. If you are preparing for a job in IT or DevOps, Linux interview questions often come up. This blog covers 70+ commonly asked questions to help you get ready.

Fun Fact – According to data, Linux powers 39.2% of the world’s top websites, runs on 85% of smartphones, and is used in all 500 of the fastest supercomputers.

Basic Level Linux Interview Questions

Here is a list of basic Linux interview questions to help you understand the operating system better.

1. What is Linux and how is it different from Windows?

Linux is a free, open-source operating system. It’s based on UNIX. Unlike Windows, Linux gives users more control and is used mainly through the terminal. It’s also widely used in servers, embedded systems, and cloud environments.

2. How do you check the current working directory?

Use the pwd command. It stands for “print working directory” and shows your location in the file system.

3. What is the difference between su and sudo?

su switches to another user account, usually root. It asks for that user’s password. sudo runs a single command as another user (often root) and needs your password, if you’re in the sudoers list.

4. How do you list all files, including hidden ones, in a directory?

Use ls -a. The -a flag shows all files, including those that start with a dot (hidden files).

5. What does the chmod command do?

chmod changes file or directory permissions. For example, chmod 755 filename gives read, write, and execute permissions to the owner, and read and execute to others.

6. How do you view the contents of a text file in the terminal?

Use commands like cat, less, or more. cat displays everything at once. less and more let you scroll through long files easily.

Note – Basic interview questions on Linux often include commands, file system structure, user management, and simple troubleshooting tasks.

Interview Questions on Linux for Freshers

Here are important Linux interview questions and answers that are commonly asked in entry-level job interviews.

7. What is the Linux file system hierarchy?

The Linux file system starts at the root (/). Everything branches from there—/home for user files, /bin for essential binaries, /etc for configurations, /var for logs, and /tmp for temporary files.

8. How do you check disk space usage in Linux?

Use df -h. The -h flag gives sizes in MB or GB, making it easier to read.

9. What is the function of the top command?

top shows running processes in real-time. It displays CPU usage, memory use, process ID, and system load. It helps spot performance issues quickly.

10. How can you create a new file from the terminal?

You can use touch filename to create an empty file. Alternatively, nano filename opens a new file for editing right away.

11. What is a process in Linux?

A process is a running instance of a program. Every command you run starts a process, and each has a unique process ID (PID).

12. How do you switch users in a Linux system?

Use the su command to switch users. For example, su john will log you into John’s account, if you have the password.

Linux Operating System Interview Questions for Experienced Professionals 

Below are advanced Linux interview questions and answers for experienced candidates working in system administration, networking, or DevOps roles.

13. How do you troubleshoot a server that is not responding to SSH?

First, I check network connectivity using ping or telnet. Then I verify the SSH port is open using nmap. If reachable, I use a console or IPMI to access the machine and check the sshd service status and logs (/var/log/auth.log or /var/log/secure). I also confirm firewall rules aren’t blocking access.

14. What are runlevels and how are they used?

Runlevels define the state of a Linux system. Older systems used numbers 0–6. For example, 0 is halt, 1 is single-user, 3 is multi-user without GUI, and 5 is with GUI. Modern systems use systemd targets like multi-user.target instead of numbered runlevels.

15. How do you create and manage cron jobs?

Use crontab -e to open the user’s cron table. Define jobs using this format:

“* * * * * /path/to/script.sh”

Each asterisk stands for minute, hour, day, month, and weekday. Use crontab -l to list jobs.

16. Explain the boot process of a Linux system.

It starts with BIOS/UEFI, which loads the bootloader (GRUB). GRUB loads the Linux kernel. The kernel mounts the root filesystem and starts init or systemd, which initializes services and brings the system to the default target.

17. What’s the difference between hard links and soft links?

Hard links point directly to the inode, and multiple hard links share the same data. Soft links (symbolic links) point to the file path, like shortcuts.

18. How do you secure a Linux server?

Disable unused services. Use SSH keys instead of passwords. Keep the system updated. Configure firewalls, use fail2ban, and audit user access regularly.

Note – Interview questions on Linux operating system for experienced professionals often include topics like shell scripting, performance tuning, networking, LVM, and troubleshooting.

Linux Interview Questions for 2 Years Experienced

• What is the difference between kill and killall?
• How have you used Linux in your current role?
• Tell me about a time you solved a Linux issue under pressure.
• How do you check which process is using the most memory?

Linux Interview Questions for 3 Years Experienced

• What does the df -h command do?
• Describe your daily responsibilities in a Linux environment.
• Share an example of a Linux script you wrote to automate a task.
• How do you check and modify user permissions?

Linux Interview Questions for 5 Years Experienced

• What is the use of the grep command?
• How have you handled critical server downtimes?
• Describe a situation where your Linux knowledge helped your team.
• How do you manage firewall rules on a Linux server?

Advanced Linux Interview Questions

This section covers advanced-level Linux OS interview questions and answers asked in senior-level technical interviews.

19. How do you isolate performance issues using vmstat and iotop?

vmstat shows memory usage, I/O wait, and CPU activity. If wa (I/O wait) is high, it’s likely a disk issue. iotop lists real-time I/O usage by process, so I can identify which process is overloading the disk.

20. What is strace and how is it used in debugging?

strace traces system calls made by a process. I use it to see what files a process opens, what it’s waiting on, or why it’s stuck. It’s helpful for spotting permission issues, failed file paths, or network errors.

21. Explain how cgroups and namespaces work in Linux.

Namespaces isolate system resources like processes, users, and mounts for containers. Cgroups control resource usage—CPU, memory, disk I/O—for each process group. Together, they power container technologies like Docker.

22. How do you apply kernel parameter changes at runtime?

Use the sysctl command. For example, sysctl -w net.ipv4.ip_forward=1 applies a new value immediately. To make it persistent, I add it to /etc/sysctl.conf or a file in /etc/sysctl.d/. Then I reload with sysctl -p.

Linux Scenario-Based Interview Questions

Here are real-world Linux scenario based interview questions and answers for experienced professionals.

23. A service fails to start – how do you debug it?

First, I run systemctl status service-name to check the basic status. Then I check logs using journalctl -xe or look under /var/log/ for detailed errors. I also verify the config files and ports.

24. A user complains of slow login – what would you check?

I check authentication delays using journalctl or /var/log/auth.log. If it’s an NFS or LDAP user, I look for network slowness or unresponsive identity services. I also check the .bashrc or .profile file for slow scripts.

25. Disk usage is 100% – what steps would you take?

I run df -h to identify full partitions. Then I use du -sh * in large directories to find what’s taking space. I delete old logs or temp files, and rotate logs using logrotate. If needed, I expand the volume.

26. A system isn’t booting properly—how would you troubleshoot?

I use a rescue or live CD to access the disk. Then I check /etc/fstab for mount errors and review boot logs in /var/log/boot.log. I also inspect GRUB settings and run fsck on suspect partitions.

Linux System Administrator Interview Questions

This section includes key interview questions of Linux system administrator roles.

27. How do you add a new user and set password policies?

Use useradd username to add a user. Then run passwd username to set the password. To set policies, edit /etc/login.defs or use chage -M 90 username to set password expiry to 90 days.

28. What are the steps to mount a new file system?

First, create a directory with mkdir /mnt/newdrive. Then use mount /dev/sdb1 /mnt/newdrive. To make it permanent, add an entry to /etc/fstab.

29. How do you schedule backups using cron?

Create a script that backs up files and add it to crontab with crontab -e. For example:
0 2 * * * /home/user/backup.sh runs it daily at 2 AM.

30. What commands do you use to monitor running processes?

I use top and htop for real-time process monitoring. ps aux gives a snapshot of all running processes. pidstat helps with detailed usage by PID.

Note – Linux sysadmin interview questions cover topics like user and group management, service control, disk management, log analysis, and basic networking.

Linux Interview Questions and Answers for Experienced L2

Here are mid-level Linux sys admin interview questions and their answers. 

31. What is the difference between systemctl and service?

systemctl is used on systemd systems and offers more control. service works with older SysVinit systems. systemctl also manages targets and dependencies.

32. How do you manage disk quotas for users?

Enable quotas in /etc/fstab by adding usrquota. Then run mount -o remount / and quotacheck -cug /, followed by quotaon /. Set limits with edquota username.

33. Explain how to configure a static IP using CLI.

Edit /etc/network/interfaces (Debian) or create a config file in /etc/sysconfig/network-scripts/ (RHEL). Define IP, gateway, and DNS. Then restart networking with systemctl restart network.

Linux Interview Questions and Answers for Experienced L3

Here are advanced-level system admin Linux interview questions and answers. 

34. How do you optimize kernel performance for high traffic servers?

I tune kernel parameters in /etc/sysctl.conf, such as increasing net.core.somaxconn, reducing swappiness, or adjusting file limits. I also use ulimit and optimize I/O schedulers.

35. What is Kdump and how do you configure it?

Kdump captures kernel crash dumps. Install kexec-tools, edit /etc/kdump.conf, and reserve memory using crashkernel=512M in GRUB. Start and enable the kdump service.

36. How do you handle SELinux-related access denials?

I check logs with ausearch -m avc or sealert -a /var/log/audit/audit.log. If needed, I adjust policies with semanage or apply contexts using restorecon.

Linux and UNIX Interview Questions

This section features commonly asked UNIX Linux interview questions and answers to help you understand the similarities, differences, and core concepts of both systems.

37. What are key differences between Linux and UNIX?

Linux is open-source and free. UNIX is mostly commercial. Linux runs on many platforms, while UNIX is mostly used on specific hardware. Linux has more community support and frequent updates.

38. How do you find the current shell in use?

Run echo $SHELL. It shows the default shell for the current user. You can also check with ps -p $$.

39. How do you search for a string inside multiple files?

Use grep -r “text” /path/. The -r flag tells grep to search recursively. For exact matches, add -w.

40. What’s the difference between sh and bash?

sh is a basic shell with fewer features. bash (Bourne Again Shell) adds arrays, better scripting tools, and command history. Most Linux systems use bash by default.

Note – Linux and UNIX interview questions often focus on command-line usage, file system structure, process management, and differences between the two systems.

Other Important Linux Interview Questions

Here are some other important interview questions on Linux operating system that don’t fall under a specific category but are still asked in many interviews.

Interview Questions for Linux Commands

This is a list of common interview questions on Linux commands.

1. What does ps aux | grep do?
2. How do you redirect output to a file?
3. What is the difference between > and >>?
4. How do you count lines, words, and characters in a file?

Linux Admin Interview Questions

Here are important Linux admin questions related to system setup, user roles, services, backups, and routine administrative tasks.

1. How do you reset a forgotten root password?
2. How do you check system load and uptime?
3. What are sticky bits and where are they used?
4. How do you limit user access to specific commands?

Note – Linux administration questions often appear in interviews for system admin, DevOps, and IT support roles.

Linux Interview Questions for DevOps

These are essential Linux OS interview questions that DevOps professionals often face in interviews.

1. How do you use shell scripting in CI/CD pipelines?
2. How do you monitor log files in real-time?
3. What is your process for automating system updates?
4. How do you manage secrets securely in a Linux environment?

Also Read - Top 25+ CI/CD Interview Questions and Answers

Linux Troubleshooting Interview Questions

Here are some important Linux operating system interview questions on troubleshooting. 

1. How do you handle a full /var directory?
2. What tools help you trace a network issue?
3. How do you find what’s consuming CPU on a server?
4. How do you debug a failed SSH connection?

Interview Questions on Linux Device Drivers

1. What is a kernel module and how do you insert it?
2. How do you debug a device driver crash?
3. What’s the difference between character and block drivers?
4. How do you assign major and minor numbers?

Linux and Networking Interview Questions

This section covers commonly asked Linux network interview questions.

1. How do you view and manage network interfaces in Linux?
2. What is the use of netstat and ss commands?
3. How do you add a persistent static route?
4. How do you troubleshoot DNS resolution issues?

Linux LVM Interview Questions

Here are important LVM interview questions to help you understand storage management, resizing, and volume handling in Linux systems.

1. How do you create a new volume group in Linux?
2. What’s the difference between lvextend and lvresize?
3. How do you take an LVM snapshot and restore it?
4. How do you check available space in a volume group?

Interview Questions on Linux Kernel

1. How do you compile a custom Linux kernel?
2. What is the role of initramfs?
3. How does the Linux kernel handle system calls?
4. What happens when you update the kernel on a live system?

Embedded Linux Interview Questions

1. What is the role of BusyBox in embedded Linux?
2. How do you reduce boot time in an embedded system?
3. What is the difference between Yocto and Buildroot?
4. How do you debug kernel panics in embedded Linux?

Interview Questions on Patching in Linux

1. How do you check which packages need updating?
2. What are the steps to apply a kernel patch?
3. How do you configure automatic security updates?
4. What is live patching and how is it done?

Linux Interview Questions on User Management

1. How do you create and manage user groups?
2. What’s the difference between /etc/passwd and /etc/shadow?
3. How do you set password expiration policies?
4. How do you lock and unlock user accounts?

Red Hat Interview Questions

This section includes key interview questions on Red Hat Linux.

1. How do you register a RHEL system to RHSM?
2. What’s the difference between YUM and DNF?
3. How do you configure firewalld in RHEL?
4. How do you troubleshoot SELinux issues?

Note – RHEL interview questions often include topics like package management with YUM/DNF, SELinux policies, systemd services, user roles, and security configurations.

Yocto Interview Questions

1. What is a recipe in Yocto?
2. How do you build a minimal image using Yocto?
3. What are layers in Yocto and how are they structured?
4. How do you debug build errors in Yocto?

Ubuntu Interview Questions

1. How do you manage software using APT?
2. What is the purpose of snap in Ubuntu?
3. How do you configure networking with Netplan?
4. How do you add a PPA and install software from it?

Company-Specific Linux Interview Questions

This section features common interview questions on Linux operating system asked by top companies.

Facebook Linux Interview Questions

1. How do you scale Linux systems for high traffic?
2. What’s your approach to monitoring server health?
3. How do you manage kernel upgrades in production?
4. How do you troubleshoot latency issues?

Google Linux Interview Questions

1. What’s your process for debugging a crashed service?
2. How do you handle large-scale patch deployments?
3. What tools do you use for log aggregation?
4. How do you ensure system reliability at scale?

IBM Linux Interview Questions

1. How do you manage system resources for multiple users?
2. What is SMT and how does Linux handle it?
3. How do you manage multi-user environments securely?
4. How do you handle hardware failures gracefully?

Linux Amazon Interview Questions

1. How do you use CloudWatch on Linux instances?
2. What are common Linux issues in EC2 and how do you fix them?
3. How do you secure a Linux-based AWS server?
4. How do you troubleshoot EBS performance on Linux?

Oracle Linux Interview Questions

1. What is Ksplice and how is it used?
2. How is Oracle Linux different from RHEL?
3. How do you configure Oracle-specific repositories?
4. What tools does Oracle Linux offer for patching?

TCS Interview Questions for Linux Administrator

1. How do you manage server hardening in Linux?
2. How do you use scripting to automate tasks?
3. How do you manage user access across multiple servers?
4. How do you back up and restore system configurations?

Note – TCS Linux admin interview questions and answers often focus on practical tasks like user management, service control, shell scripting, and basic troubleshooting.

How to Prepare for Linux Interview?

Here are some helpful tips that you can follow to prepare for your Linux interview. 

• Master basic commands – Know how to use ls, cd, cat, grep, find, and chmod.
• Understand file system structure – Learn what each directory (like /etc, /var, /home) is used for.
• Practice user and permission management – Know how to add users, groups, and set correct file permissions.
• Get comfortable with troubleshooting – Simulate issues and solve them using logs, top, and netstat.
• Read man pages – Use man to understand how commands work in detail.
• Document what you learn – Keep a simple log of errors and solutions.
• Stay updated – Learn changes in newer versions of Linux and system tools.
• Interview questions – Practice common Linux interview questions and answers. 

Wrapping Up

We hope these Linux interview questions and answers help you feel more confident during your job search. Practice regularly, understand the concepts, and stay updated with the latest tools.

Looking for Linux jobs in India? Try Hirist – an online job portal built for tech professionals. Find the top Linux job opportunities and apply easily.

FAQs

What are the basic Linux commands for interview?

Common Linux commands asked in interview include ls, pwd, cd, chmod, ps, kill, grep, top, df, and du. These commands are essential for file handling, process management, and system monitoring.

Are Linux experience interview questions tough?

They can be challenging, especially for roles involving performance tuning, kernel-level tasks, or large-scale system management. With hands-on practice, these questions become manageable.

What is the average salary for Linux professionals in India?

According to AmbitionBox, Linux Administrator in India typically earns between ₹2.3 Lakhs and ₹9 Lakhs per year, depending on their experience level from 1 to 7 years.

Which top companies hire Linux professionals in India?

TCS, Infosys, Wipro, IBM, Google, Amazon, Oracle, and HCL actively hire candidates with strong Linux skills for admin, DevOps, and infrastructure roles.

What are some tips to answer Linux interview questions confidently?

• Practice daily on a live terminal
• Keep your answers short and accurate
• Share real-life experiences when possible
• Know the basics really well

What is basic knowledge of Linux?

Basic Linux knowledge includes understanding file system structure, using the terminal, managing files and directories, working with users and permissions, and running basic commands like ls, cd, chmod, and ps.

What is the full form of Linux?

Linux doesn’t have a full form. It is named after its creator, Linus Torvalds, combined with Unix, the system it was inspired by.

What is LVM in Linux interview questions?

In interviews, LVM (Logical Volume Manager) refers to a system used for flexible disk management. Candidates may be asked how to create, extend, or snapshot logical volumes using commands like pvcreate, vgcreate, lvcreate, and lvextend.