Top 45+ Must-Know Linux Commands Interview Questions and Answers for 2025

Linux command interview questions often test practical knowledge of essential commands and their real-world applications.

In this blog, you will look at comprehensive Linux commands, interview questions and answers to help you prepare. This blog equips you with key commands, scenarios, and troubleshooting tips to ace Linux interviews.

Essential Linux Commands Interview Questions and Answers

This section covers key Linux commands, interview questions and answers, focusing on the fundamental concepts you need to understand when starting with Linux. This section is designed for beginners, so no prior knowledge is needed—just a curiosity to learn and practice! 

1. What is Linux, and how does it differ from other operating systems?

Linux is an open-source, Unix-like operating system known for its stability, security, and flexibility, powering everything from servers and supercomputers to embedded systems and smartphones. Unlike proprietary operating systems like Windows or macOS, Linux is free to use and modify, with a strong community-driven development model. 

The key differences between Linux and other operating systems include:

Also Read: Functions of Operating System: Features, Uses, Types

2. What is the Linux Kernel, and can it be modified?

The Linux Kernel is the core of the Linux operating system, managing hardware, memory, and system processes while acting as a bridge between software and hardware. Being open-source, it allows users to modify and recompile it for specific needs.

For example, cloud providers often optimize the kernel for performance and security in virtualized environments, while embedded systems developers create lightweight, custom kernels for IoT devices. This flexibility makes Linux highly adaptable across different industries and use cases.

3. What is LILO, and how is it used in Linux?

LILO (LInux LOader) was an early bootloader for Linux, responsible for loading the kernel at startup. However, it is now largely obsolete, replaced by more advanced bootloaders like GRUB and systemd-boot, which offer better support for modern hardware, multiple OS booting, and advanced configuration options.

It can be configured to handle multiple operating systems on a single machine and allows users to select which OS to boot from during startup.

4. What are the core components of the Linux operating system?

The Linux operating system consists of several core components that work together to provide a stable, efficient environment:

• Kernel: Manages hardware resources and enables communication between software and hardware.
• Shell: Acts as a bridge between users and the system, interpreting commands.
• System Libraries: Provide essential functions that allow applications to interact with the system.
• System Tools: Offer utilities for system management, like file handling and process monitoring.
• User Interface: Enables user interaction, whether through a command line or a graphical desktop.

5. What are the different types of shells available in Linux?

In Linux, shells are command-line interfaces that allow users to interact with the system. This is a very generic statement. Consider giving an example of a unique feature each shell offers, such as Zsh's powerful tab completion or Fish's autosuggestions, to make this information more concrete. The most common types are:

• Bash (Bourne Again Shell): The default and most widely used shell in Linux.
• Zsh (Z Shell): An enhanced version of Bash with more features like better tab completion.
• Tcsh (TENEX C Shell): A shell that provides improved features for C-shell users.
• Fish (Friendly Interactive Shell): Known for its user-friendly interface and auto-suggestions.
• Ksh (Korn Shell): A shell that is a superset of the Bourne shell, offering more features for script writing.

Also Read: 40 Scripting Interview Questions & Answers [For Freshers & Experienced]

6. What is Swap Space in Linux, and why is it important?

Swap space in Linux is a designated area on a hard drive that acts as virtual memory when the physical RAM is fully used. It allows the system to move inactive data from RAM to the hard drive, freeing up space in RAM for active processes.

Why is it important?

Swap space is critical for ensuring that the system does not crash when the available RAM is exhausted. It helps improve stability, allowing Linux to handle large workloads and maintain performance even under high memory demand. 

Without sufficient swap space, the system might become slow or even fail to function when RAM usage peaks.

7. How does BASH differ from DOS command-line interface?

BASH (Bourne Again Shell) and DOS (Disk Operating System) command-line interfaces are both used for interacting with a system through text commands, but they differ significantly in capabilities and design. The key differences include:

8. Which command would you use to check memory usage in Linux?

To check memory usage in Linux, the free command is commonly used. Running free -h will display memory usage in a human-readable format, showing total, used, free, and available memory. You can also use the top or htop commands to monitor real-time memory and CPU usage.

9. What are file permissions in Linux, and how do they work?

In Linux, file permissions determine who can access or modify a file and to what extent. These permissions are essential for system security and proper user access management. The three main types of file permissions are:

• Read (r): Allows the user to view the contents of a file.
• Write (w): Allows the user to modify the file.
• Execute (x): Allows the user to run the file as a program.

Each file has three sets of permissions: owner, group, and others, and they can be modified using the chmod command to ensure proper access control. 

10. What are inodes and process IDs (PIDs) in Linux?

An inode is a data structure in Linux that stores information about a file or directory, excluding its name. It contains metadata like permissions, ownership, size, and the location of the file's data on the disk. Inodes are essential for the system to efficiently manage files and directories.

A Process ID (PID) is a unique number assigned by the system to each running process. It allows the system to track and manage processes, ensuring they do not interfere with one another. PIDs are crucial for process management, allowing tasks such as terminating or prioritizing processes to be carried out effectively.

11. Which commands are commonly used for directory navigation in Linux?

In Linux, directory navigation commands allow users to move around the file system and access various files and folders. Some of the most commonly used commands for directory navigation include:

• cd (Change Directory): Used to navigate between directories.
• pwd (Print Working Directory): Displays the current directory.
• ls (List): Lists the contents of a directory.
• mkdir (Make Directory): Creates a new directory.
• rmdir (Remove Directory): Removes an empty directory.

These commands are essential for working with files and folders within the Linux file system.

12. What is a virtual desktop in Linux, and how does it improve workflow?

A virtual desktop in Linux is a feature that allows users to create multiple workspaces, enabling them to organize their tasks across different desktops. This can be especially helpful for multitasking or managing different types of work.

How does it improve workflow?

Virtual desktops enhance productivity by providing a clutter-free environment where users can switch between workspaces without cluttering a single screen. You can keep your coding tasks in one desktop, while your web browsing or reference materials can be on another, reducing distractions and improving focus.

13. What are the different modes available in the vi editor?

The vi editor, a powerful text editor in Linux, operates in different modes that cater to various editing tasks. The key modes are:

• Normal Mode: The default mode used for navigation and issuing commands.
• Insert Mode: Used for typing text into the file.
• Command Mode: Used for executing commands like saving, quitting, and searching.
• Visual Mode: Used to highlight text for editing, copying, or deleting.

Each mode provides a different set of capabilities, and understanding how to switch between them is essential for efficient use of the editor.

14. How can you rename a file in Linux?

To rename a file in Linux, you use the mv (move) command. Here's the syntax: 

mv oldfilename newfilename

This command moves (or renames) the file from oldfilename to newfilename.

15. How do you redirect the output of a command to a file in Linux?

In Linux, you can redirect the output of a command to a file using the > or >> operators. Here's an example: 

command > outputfile.txt

This will redirect the standard output of the command to the file outputfile.txt, overwriting the file if it already exists. To append the output instead of overwriting, use: 

command >> outputfile.txt

16. Which command lists all currently mounted filesystems?

To list all currently mounted filesystems in Linux, you can use the mount command: 

mount

This will display a list of all mounted filesystems along with their details, including the device name and mount point.

17. How do you find the exact location of a specific file in Linux?

To find the exact location of a specific file in Linux, you can use the find command: 

find / -name "filename"

This searches the entire file system starting from the root (/) for the file named "filename" and returns its exact path.

18. Which command allows you to copy files to an external storage device in Linux?

To copy files to an external storage device in Linux, you can use the cp command. For example: 

cp /path/to/file /media/usb/

This copies the file from its original location to the external storage device (mounted at /media/usb/).

Also Read: Understanding Storage Virtualization: How It Works, Benefits, and Challenges

19. How can you check which shell you are currently using?

To check which shell you are currently using, you can run the following command: 

echo $SHELL

This command prints the path of the current shell you are using, such as /bin/bash or /bin/zsh.

20. What command sorts the contents of a text file in ascending order?

To sort the contents of a text file in ascending order, use the sort command: 

sort filename.txt

This sorts the lines of filename.txt in ascending order and displays them. To save the sorted output to a new file, use the > redirection: 

sort filename.txt > sortedfile.txt

Also Read: A Complete Guide to Master Linux Commands for DevOps in 2025

Now that you've got the basics down, let's dive into the intermediate commands that will truly test your Linux expertise.

Intermediate-Level Linux Commands Interview Questions and Insights

In this section, you’ll explore intermediate-level Linux commands that focus on process management, file system handling, and networking. These topics are crucial for professionals who have a basic understanding of Linux but want to improve their skills. Let’s dive in and expand your command-line toolkit.

21. What are daemons in Linux, and how do they function?

Linux Daemons are background processes running continuously to manage system tasks or provide services. They typically start when the system boots up and run until the system shuts down.

How do they function?

Daemons are usually started during the system boot sequence and continue running without user interaction. They handle tasks such as monitoring system health, managing hardware, or providing network services. 

Examples include sshd (for secure shell access) and cron (for scheduled tasks). Daemons usually run with minimal resources and operate in the background, often without direct user control.

22. What are the different states of a process in Linux?

In Linux, processes can be in various states during their lifecycle. These states include:

• Running (R): The process is currently executing or is ready to execute.
• Sleeping (S): The process is waiting for an event or condition, such as user input or I/O.
• Stopped (T): The process has been stopped, usually by a signal.
• Zombie (Z): The process has completed but still has an entry in the process table.
• Idle (I): The process is not executing any tasks but is still running.

These states help determine the current status of a process and are critical for system performance and troubleshooting.

23. Which system calls are used for process management in Linux?

In Linux, several system calls are used to manage processes. Some of the key ones include:

• fork(): Creates a new process by duplicating the calling process.
• exec(): Replaces the current process with a new process.
• wait(): Makes a process wait until one of its child processes terminates.
• exit(): Terminates the calling process.
• kill(): Sends a signal to terminate or manipulate a process.

These system calls provide essential control over process creation, execution, and termination in a Linux environment.

24. How do you terminate a running process using command-line tools?

To terminate a running process in Linux, you can use the kill command followed by the process ID (PID): 

kill PID

If the process does not terminate with a regular signal, you can forcefully kill it using: 

kill -9 PID

This sends a SIGKILL signal, which immediately terminates the process without allowing it to clean up resources.

25. What is the difference between a zombie process and an orphan process?

Both zombie and orphan processes are related to process management, but they differ in their behavior and causes. 

Here’s how they compare:

26. How do you check system performance metrics in Linux?

To check system performance metrics in Linux, you can use a variety of commands that give insights into CPU, memory, disk, and network usage. Some of the most commonly used commands include:

• top: Displays real-time information about system processes, CPU usage, and memory.
• htop: An enhanced version of top, providing a more user-friendly interface.
• vmstat: Displays information about system memory, processes, and hardware.
• iostat: Reports on CPU and input/output statistics for devices.
• free: Shows memory usage, including swap space.

These tools help monitor system performance and diagnose issues, ensuring the system runs smoothly.

27. Which command lists all active processes running on a Linux system?

To list all active processes running on a Linux system, you can use the ps command with the aux option: 

ps aux

This will display a comprehensive list of all active processes, including their PID, memory usage, and running time. You can also use top for real-time updates of active processes.

28. How do you schedule a recurring task in Linux using cron?

To schedule a recurring task in Linux using cron, you need to add a cron job by editing the crontab file: 

crontab -e

Once the crontab is open, you can add a line specifying the schedule and the command to run. For example, to run a script every day at 2:00 AM: 

0 2 * * * /path/to/script.sh

The format is: 

minute hour day month day-of-week command-to-run. 

This allows you to automate repetitive tasks.

29. What is the difference between the cron and at commands in task scheduling?

Both cron and at are used to schedule tasks, but they serve different purposes. 

Here's how they compare:

30. How does the grep command work, and what are its most common options?

The grep command in Linux is used to search for patterns within files. It outputs lines that match a specified pattern, making it a powerful tool for searching logs, configuration files, and other text-based data.

Common options for grep include:

• -i: Ignores case distinctions (e.g., grep -i 'error' will match "Error" and "error").
• -r or -R: Recursively searches through directories.
• -v: Inverts the match, showing lines that do not match the pattern.
• -l: Lists only the names of files that contain the matching pattern.
• -n: Displays line numbers along with the matching lines.

For example: 

grep -i 'error' logfile.txt

This command will search for the word "error" in logfile.txt, regardless of case.

31. What are regular expressions, and how are they used in Linux commands?

Regular expressions (regex) are patterns used to match and manipulate text. They allow you to search for specific strings or patterns within a file, validate input, and perform complex text processing tasks.

How are they used?

In Linux, regular expressions are widely used with commands like grep, sed, and awk. For example, grep uses regex to search for patterns within files. You can use metacharacters like . (any character), * (zero or more occurrences), and [] (character classes) to form more advanced search patterns. 

Here’s a simple example with grep: 

grep '^[A-Za-z]' filename.txt

This searches for lines starting with any alphabetic character.

32. How can you search for a specific word within a file in Linux?

To search for a specific word within a file, you can use the grep command: 

grep 'word' filename.txt

This command searches for the word "word" in filename.txt and displays all lines containing that word.

33. What does the cut command do, and how is it used for text processing?

The cut command in Linux is used for text processing, specifically to extract specific sections from each line of a file or input. It’s useful when you need to isolate columns of data from a text file or output.

How is it used?

The cut command works by specifying a delimiter (such as a space, comma, or tab) and selecting which field or columns to extract. 

For example, to extract the second column from a file where spaces separate columns: 

cut -d ' ' -f 2 filename.txt

This will display the second field (column) of each line in filename.txt.

34. How can you merge the contents of multiple files into one file?

To merge the contents of multiple files into one file, you can use the cat command with output redirection: 

cat file1.txt file2.txt > mergedfile.txt

This will concatenate the contents of file1.txt and file2.txt and save them in mergedfile.txt. 

If you want to append to an existing file, use >> instead of >: 

cat file1.txt file2.txt >> existingfile.txt

Also Read: Command Line Arguments in Java [With Example]

Now that you've mastered the basics and intermediate commands let's explore the advanced commands that will take your Linux skills to the next level.

Advanced Linux Commands Interview Questions: In-Depth Analysis

In this section, you’ll explore advanced topics like system performance tuning, in-depth debugging methods, and command-line automation—skills crucial for professionals working with complex Linux command scenarios. These Linux command interview questions and answers will help you refine your expertise. 

35. How do you modify file permissions in Linux, and what is the chmod command?

To modify file permissions in Linux, you use the chmod (change mode) command. This command allows you to define who can read, write, and execute a file. Permissions are set using either symbolic notation (r, w, x) or octal notation (0-7).

For example, to give read, write, and execute permissions to the owner, and read and execute permissions to others: 

chmod 755 filename

Alternatively, you can use symbolic notation: 

chmod u+x filename

This grants execute permission to the owner. The chmod command is a powerful way to control file access and ensure security.

36. What is the difference between chown and chgrp in Linux?

Both chown and chgrp are commands used to change ownership of files, but they differ in their functionality. 

Here's how they compare:

chown allows you to modify both user and group ownership in one command, while chgrp is used when only the group needs to be changed.

37. Which command is used to check available disk space on a Linux system?

To check available disk space in Linux, you can use the df (disk free) command. For a human-readable format, use the -h option: 

df -h

This command displays the available and used disk space for all mounted filesystems, including their size, used space, and available space.

38. How do gzip and bzip2 differ in file compression?

Both gzip and bzip2 are used for file compression, but they differ in speed, compression ratio, and the algorithms they use.

In summary, gzip is faster but less efficient, while bzip2 offers better compression at the cost of speed.

39. How do you create and manage symbolic links in Linux?

To create a symbolic link in Linux, you use the ln -s command, which creates a link to another file or directory: 

ln -s /path/to/target /path/to/link

This command creates a symbolic (soft) link that points to the target file or directory.

To manage symbolic links, you can use commands like ls -l to list the links and their targets, rm to remove a symbolic link, and unlink to remove a symbolic link without affecting the original file: 

rm /path/to/symlink

Symbolic links are useful for creating shortcuts and managing files across different locations in the file system without duplicating data.

40. What is the correct command to add a new user in Linux?

To add a new user in Linux, you can use the useradd command followed by the username: 

sudo useradd username

This creates a new user account. To set a password for the new user, use the passwd command: 

sudo passwd username

This will prompt you to enter and confirm the password for the newly created user.

41. What is a virtual desktop, and how is it beneficial for Linux users?

A virtual desktop in Linux is a feature that allows users to create multiple workspaces, giving them more room to organize their tasks and programs.

How is it beneficial?

For Linux users, virtual desktops are a great way to increase productivity and reduce clutter. You can separate different tasks, such as coding, browsing, and email, into separate desktops. This allows you to switch between tasks without closing or minimizing windows, making multitasking more efficient. 

Virtual desktops improve focus by providing a cleaner and more organized workspace.

42. How can you efficiently edit large files using the vi or nano editor?

When editing large files in vi or nano, it's important to use efficient navigation and search techniques to avoid unnecessary delays. In vi, use commands like :set number to show line numbers and :search to jump to a specific location. To efficiently move through the file, use gg to go to the beginning, and G to jump to the end.

In nano, use Ctrl+_ to jump to a specific line number and Ctrl+W to search for text. Both editors allow you to quickly navigate large files without slowing down your workflow.

43. How do you find and replace specific text across multiple files in Linux?

To find and replace specific text across multiple files in Linux, you can use the sed command with the -i option for in-place editing. For example: 

sed -i 's/oldtext/newtext/g' *.txt

This command will search for "oldtext" and replace it with "newtext" in all .txt files in the current directory. The g flag ensures that all instances of the word are replaced in each file.

44. Which command is used to count the number of words, lines, and characters in a file?

To count the number of words, lines, and characters in a file, you can use the wc (word count) command: 

wc filename.txt

This will display three numbers: the line count, word count, and character count. To count only one of these, you can use specific options, like -l for lines, -w for words, and -c for characters: 

wc -w filename.txt

45. What is the difference between sed and awk, and when should each be used?

Both sed and awk are powerful text processing tools in Linux, but they are used for different tasks. 

Here’s a breakdown of how they compare:

Use sed when you need simple substitutions or line editing, and awk when you need to process data in columns or perform complex tasks like summing values.

46. What is the purpose of the nohup command, and when is it useful?

The nohup command is used to run a process in the background, even after you log out of the system. It ensures that the process will continue running regardless of user session termination.

When is it useful?

It’s particularly helpful when running long processes, like backups or data transfers, that need to continue even if you’re disconnected or logged out. For example, to run a command in the background: 

nohup command & 

This keeps the process running after you log out and redirects output to nohup.out.

47. How do you securely transfer files between remote Linux systems?

To securely transfer files between remote Linux systems, you can use the scp (secure copy) command, which encrypts the data during transmission. 

The basic syntax is: 

scp /path/to/localfile username@remotehost:/path/to/remotefile

This copies a local file to a remote system securely. You can also use rsync with SSH for more advanced file transfer options, such as incremental copying and bandwidth limitation: 

rsync -avz -e ssh /path/to/localfile username@remotehost:/path/to/remotefile

48. Which commands help in identifying where a particular file is stored on a Linux system?

To find where a particular file is stored on a Linux system, you can use the find or locate command.

• find is used for searching the entire filesystem or specific directories: 

find / -name "filename"

• locate is faster, as it uses a database of files: 

locate filename

Both commands help you identify the location of files quickly, with find offering more control over search parameters.

49. How can you sort text data based on multiple columns in a file?

To sort text data based on multiple columns in Linux, you can use the sort command with the -k option. 

For example, to sort by the second column and then by the first column: 

sort -k2,2 -k1,1 filename.txt

This sorts the file filename.txt by the second column and, if there are duplicates, by the first column. You can also specify sorting order with -n for numeric sorting or -r for reverse order.

50. Why is the tar command widely used in Linux, and what are its key options?

The tar command in Linux is widely used for creating and extracting compressed archives. It's a versatile tool that handles not only compression but also file backup and packaging.

Key options:

• -c: Create a new archive.
• -x: Extract files from an archive.
• -f: Specify the filename of the archive.
• -v: Verbose mode, shows the files being archived or extracted.
• -z: Compress the archive using gzip.
• -j: Compress the archive using bzip2.
• -J: Compress the archive using xz.

For example, to create a tar.gz archive: 

tar -czvf archive.tar.gz /path/to/files

Also Read: DevOps Tutorial – Introduction, Benefits, Challenges & Lifecycle

Now that you've mastered the commands, let's focus on strategies that will help you shine in your Linux commands interview.

Strategies to Succeed in Your Linux Commands Interview

Preparing for a Linux commands interview requires more than just memorizing commands. You need to be ready to explain your thought process, demonstrate problem-solving skills, and show that you can efficiently use the command-line interface. 

Here are some practical strategies to help you succeed:

• Practice with Real-Life Examples: Don't just memorize commands—use them in real scenarios. For example, practice navigating the file system with commands like ls, cd, and pwd. Try working with grep to search for patterns or use find to locate files in large directories. The more you practice, the more confident you’ll be during the interview.
• Understand the Logic Behind Commands: It’s not enough to know what a command does—you should understand why you’re using it. When asked a question about a specific Linux command, break it down step by step. For example, if asked about chmod, explain how the octal values correspond to read, write, and execute permissions.
• Avoid Over-Explaining: While it’s important to explain your reasoning, avoid rambling. Focus on providing concise and clear answers, as interviewers often look for efficiency, not long-winded explanations. When answering Linux commands interview questions and answers, aim for a balance between detail and brevity.
• Know Key Commands and Their Options: Focus on mastering the most common commands that come up in Linux commands interview questions. Be ready to explain the options that modify the behavior of commands like ls, cp, mv, and grep. For example, ls -l gives detailed information, while ls -a shows hidden files. Understand these variations and when to use them.
• Use the Right Tools for the Job: Understand which tools are best suited for specific tasks. For instance, find is great for locating files, while locate is faster but requires a pre-built database. Interviewers want to see that you can efficiently choose the right tool for each situation.
• Demonstrate Problem-Solving Skills: Linux interviews often focus on practical problem-solving. If you're asked to find and replace text in multiple files, explain your thought process. Show that you know which tools to use and why, whether it’s sed, awk, or grep. Walk through the logic and give examples.
• Be Prepared for Scenario-Based Questions: Many Linux interviews include hypothetical scenarios. For example, an interviewer might ask how you would optimize a server’s performance or recover a crashed system. Think through the steps clearly and methodically. Show your ability to diagnose issues and apply the appropriate commands to resolve them.

Key Mistakes to Avoid

• Skipping Basics: Don’t skip over basic commands or concepts, even if they seem too simple. Mastering the foundational Linux commands is essential before tackling more advanced topics.
• Lack of Preparation for Edge Cases: Interviewers may test your ability to handle edge cases or unusual scenarios. Always prepare for the unexpected, like handling files with unusual characters or debugging an unresponsive process.
• Overlooking Permissions and Ownership: File permissions, ownership, and group management are critical topics. Make sure you can confidently explain and use commands like chmod, chown, and chgrp.

By following these strategies, practicing regularly, and refining your approach, you will be well-prepared to handle Linux commands, interview questions and answers with ease and confidence.

How Can upGrad Enhance Your Linux Expertise?

upGrad can help you elevate your Linux expertise and better prepare for Linux commands interview questions and answers by offering structured learning paths that combine theoretical knowledge with real-world applications. 

By focusing on key areas such as system administration, automation, and cloud integration, you'll gain a deep understanding of how Linux operates in various environments.

Here are some of the top courses to choose from: 

• Professional Certificate Program in Cloud Computing and DevOps
• AI-Powered Full Stack Development Course by IIITB
• Cloud Engineering Bootcamp
• Advanced Generative AI Certification Course

You can also get personalized career counseling with upGrad to guide your career path, or visit your nearest upGrad center and start hands-on training today! 

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