65 Linux Commands Interview Questions to Ask Candidates

Recruiting the right Linux administrators can be challenging, especially when it comes to assessing their technical skills. Asking the right Linux command interview questions helps you identify candidates who truly understand the system, increasing your chances of a successful hire skills required for Linux administrator.

This blog post covers a comprehensive range of Linux command interview questions tailored for various experience levels and specialties. From questions for junior administrators to those evaluating shell scripting expertise and situational problem-solving skills, we've got you covered.

By using this guide, you enhance your interview process, ensuring you identify the best candidates for your needs. Additionally, consider using our Linux online test before interviews to further gauge applicants' proficiency.

Table of contents

Top 8 Linux Commands questions to ask in interviews

To ensure your candidates have the essential Linux command skills needed for the job, consider asking them some of these top interview questions. This list will help you gauge their practical knowledge and problem-solving abilities in a Linux environment.

1. What does the 'cd' command do in Linux?

The 'cd' command in Linux is used to change the current directory. For instance, if you're in the home directory and want to navigate to a subdirectory called 'Documents', you would use 'cd Documents'.

Look for candidates to explain that the 'cd' command can be used with both relative and absolute paths, providing examples for each. This shows they have practical experience navigating the filesystem.

2. How would you check the available disk space on a Linux system?

To check the available disk space on a Linux system, you can use the 'df' command, which stands for 'disk free'. This command provides details about the file system disk space usage.

A good response will mention using 'df -h' for a more human-readable format, showing the space in GB or MB instead of blocks. This demonstrates their ability to interpret and present data clearly.

3. What is the purpose of the 'chmod' command?

The 'chmod' command in Linux is used to change the file permissions. This command allows you to define who can read, write, or execute a file or directory.

Candidates should be able to explain the different permission settings (read, write, execute) and how they can be applied using both symbolic and numeric modes. This indicates their familiarity with managing file security.

4. How do you view the contents of a file in Linux?

There are several commands to view the contents of a file in Linux, including 'cat', 'less', 'more', and 'tail'. Each command has its own use case depending on the size of the file and the information needed.

Candidates should detail the differences, such as 'cat' displaying the entire file at once, 'less' and 'more' allowing for paginated viewing, and 'tail' showing the last few lines. This shows their versatility in handling different scenarios.

5. Explain how you would find a specific string in a file.

To find a specific string in a file, you can use the 'grep' command. For example, 'grep "search_string" filename' will search for 'search_string' within 'filename' and display the matching lines.

An ideal candidate will know additional options such as 'grep -i' for case-insensitive searches or 'grep -r' to search recursively in directories. This demonstrates a deeper understanding of how to utilize 'grep' effectively.

6. How do you list all the files in a directory, including hidden files?

To list all the files in a directory, including hidden files, you would use the 'ls -a' command. Hidden files in Linux start with a dot (.) and 'ls -a' ensures they are displayed as well.

Candidates should also mention 'ls -l' to get a detailed listing including file permissions, ownership, and modification dates. This shows they can extract comprehensive file information.

7. What is the purpose of the 'ps' command?

The 'ps' command is used to display information about the currently running processes. It provides details such as process ID (PID), terminal associated with the process, CPU usage, and more.

Look for candidates who can explain using 'ps aux' to get a more comprehensive list of all processes and their attributes. This shows their ability to monitor and manage system processes effectively.

8. How do you check the current system uptime in Linux?

To check the current system uptime, you can use the 'uptime' command. This command provides information on how long the system has been running, along with the current time, number of users, and system load averages.

A strong response will include an explanation of the load average and its importance in understanding system performance. This indicates the candidate's ability to assess system health.

20 Linux Commands interview questions to ask junior administrators

To assess the practical skills of junior Linux administrators, use these 20 command-line questions during interviews. These questions help evaluate candidates' familiarity with essential Linux operations and their ability to perform basic system management tasks.

1. How would you create a new user account in Linux?
2. Explain the difference between relative and absolute paths.
3. What command would you use to change file ownership?
4. How can you schedule a task to run automatically at a specific time?
5. Describe how you would compress and decompress files in Linux.
6. What's the purpose of the 'grep' command and how would you use it?
7. How do you check and manage running processes in Linux?
8. Explain how to set up a basic firewall using iptables.
9. What command would you use to check system resource usage?
10. How do you create and manage symbolic links?
11. Describe the process of mounting and unmounting file systems.
12. What's the difference between 'sudo' and 'su' commands?
13. How would you search for files larger than a specific size?
14. Explain how to redirect output to a file and append to an existing file.
15. What command would you use to view real-time log entries?
16. How do you check and modify file permissions recursively?
17. Describe how to use the 'find' command to locate files.
18. What's the purpose of the '/etc/fstab' file and how would you edit it?
19. How can you check and manage available swap space?
20. Explain how to use 'tar' for backing up and restoring files.

10 intermediate Linux Commands interview questions and answers to ask mid-tier administrators

To ensure your mid-tier Linux administrator candidates have the right expertise, consider asking them these intermediate Linux command questions. These questions are designed to gauge their problem-solving skills and practical knowledge, making it easier for you to identify the best fit for your team.

1. How would you monitor real-time system performance in Linux?

Candidates might mention tools like 'top' and 'htop' for monitoring real-time system performance. These commands display a dynamic view of the system, including CPU usage, memory usage, and load average.

Another option is using 'vmstat' for memory statistics and 'iostat' for I/O statistics. These tools provide a more detailed breakdown of system resource usage, which can be crucial for performance tuning.

Look for candidates who can explain the importance of monitoring different metrics and how they would use this information to diagnose and resolve performance issues.

2. Explain how you would manage background and foreground processes in Linux.

Managing background and foreground processes involves using commands like 'bg', 'fg', and 'jobs'. 'bg' sends a process to the background, 'fg' brings it to the foreground, and 'jobs' lists all jobs started in the current session.

For example, if a task is running in the foreground and you need to free up the terminal, you can suspend it using Ctrl+Z and then use 'bg' to continue running it in the background.

Ideal responses should highlight an understanding of process management and mention scenarios where handling background processes is necessary, such as running long scripts or maintenance tasks.

3. How would you manage software packages on a Linux system?

Candidates should mention package management tools like 'apt' for Debian-based systems or 'yum' for Red Hat-based systems. These tools allow you to install, update, and remove software packages.

For example, using 'apt', you can run 'sudo apt-get update' to refresh the package list and 'sudo apt-get install [package_name]' to install a new package. Similarly, 'yum' uses commands like 'yum install [package_name]' for installation.

Strong candidates will also touch on the importance of keeping software up to date for security and functionality reasons, and might also mention manual methods using 'dpkg' or 'rpm'.

4. Describe how you would analyze and troubleshoot network connectivity issues in Linux.

Analyzing network connectivity issues typically involves using commands like 'ping', 'traceroute', and 'netstat'. 'ping' checks the availability of a host, 'traceroute' maps the route packets take, and 'netstat' provides network statistics.

Candidates might also use 'ifconfig' or 'ip' for interface configurations and 'nslookup' or 'dig' for DNS troubleshooting. These tools collectively help diagnose where the problem lies, whether it's a DNS issue, routing problem, or interface misconfiguration.

Look for candidates who can explain a step-by-step approach to isolating and resolving connectivity issues, showing a logical troubleshooting process.

5. How do you manage user permissions for files and directories in Linux?

Managing user permissions typically involves using 'chmod' for changing file permissions and 'chown' for changing ownership. Permissions are categorized into read, write, and execute for the user, group, and others.

For instance, 'chmod 755 [file]' sets the file's permissions to read, write, and execute for the owner, and read and execute for the group and others. 'chown user:group [file]' changes the file's owner and group.

Candidates should demonstrate an understanding of the permission model and the implications of different permission settings. Look for an explanation of real-world scenarios where managing permissions is crucial, like securing sensitive data.

6. What steps would you take to secure a Linux server?

Securing a Linux server involves several practices such as regular updates, configuring a firewall, disabling unnecessary services, and using strong passwords. Tools like 'iptables' or 'ufw' can be used for configuring firewalls.

Candidates should also mention the importance of monitoring logs, setting up intrusion detection systems, and implementing SSH keys for secure remote access. Regular audits and compliance checks are also critical components.

Strong responses will cover a multi-layered approach to security, emphasizing the importance of both proactive and reactive measures. Look for a clear understanding of best practices and the ability to apply them.

7. Explain how you would handle disk management and partitioning in Linux.

Disk management and partitioning can be handled using tools like 'fdisk', 'parted', or 'lsblk' for listing block devices. 'fdisk' and 'parted' are used for creating and managing partitions.

For example, using 'fdisk', you can create a new partition by selecting the disk and following the prompts to define the partition size and type. 'parted' offers a more advanced interface with support for additional filesystem types.

Candidates should explain the importance of planning disk partitions based on the system's needs and might also touch on Logical Volume Manager (LVM) for more flexible disk management.

8. How do you automate repetitive tasks in Linux?

Automating repetitive tasks in Linux can be accomplished using shell scripting or tools like 'cron' for scheduling jobs. Shell scripts allow for the automation of complex sequences of commands.

With 'cron', you can schedule tasks to run at specific intervals, such as daily backups or periodic system updates. The 'crontab' file is used to define these schedules and the commands to execute.

Look for candidates who can not only write basic scripts but also understand how to use 'cron' effectively. They should mention error handling and logging as part of their automation strategy.

9. What strategies would you use for effective log management in Linux?

Effective log management involves using tools like 'logrotate' to manage log file sizes and 'rsyslog' for system logging. 'logrotate' helps to automatically compress, remove, and manage log files to prevent them from consuming excessive disk space.

Candidates might also mention setting up centralized logging solutions like ELK Stack (Elasticsearch, Logstash, Kibana) to aggregate and analyze logs from multiple sources, making it easier to monitor and troubleshoot issues.

Ideal candidates will emphasize the importance of regular log reviews, setting up alerts for critical events, and ensuring compliance with data retention policies.

10. How would you check for and fix filesystem errors in Linux?

To check for and fix filesystem errors, 'fsck' (File System Consistency Check) is commonly used. Running 'fsck' on a filesystem can detect and repair inconsistencies.

For example, 'sudo fsck /dev/sda1' would check and fix errors on the specified partition. It is crucial to unmount the filesystem before running 'fsck' to avoid data corruption.

Strong responses should demonstrate an understanding of when and how to use 'fsck', potential risks involved, and the importance of regular maintenance to prevent filesystem errors.

12 Linux Commands interview questions about shell scripting

To assess a candidate's proficiency in shell scripting, a crucial skill for Linux administrators, use these 12 interview questions. They cover essential concepts and practical applications, helping you evaluate the applicant's ability to automate tasks and manage systems efficiently.

1. How would you write a shell script to find and delete all files older than 30 days in a specific directory?
2. Explain the difference between $@ and $* in shell scripting.
3. Write a one-line command to replace all occurrences of 'foo' with 'bar' in all .txt files in the current directory and its subdirectories.
4. How would you create a shell script that takes a filename as an argument and creates a backup of that file?
5. Explain the purpose of the 'set -e' command in a shell script.
6. Write a shell function that checks if a given number is prime.
7. How would you use a 'for' loop to rename all .jpg files in a directory to have a .png extension?
8. Explain the difference between single quotes and double quotes in shell scripting.
9. Write a shell script that counts the number of lines in each file in a directory and outputs the results sorted by line count.
10. How would you use 'sed' to extract all email addresses from a log file?
11. Explain the purpose of the 'shift' command in shell scripting.
12. Write a shell script that monitors system load and sends an alert if it exceeds a certain threshold.

8 Linux Commands interview questions and answers related to file management

To assess candidates' skills in managing files on a Linux system, use these interview questions. These questions will help you gauge whether applicants can effectively navigate and manipulate the file system, ensuring they have the necessary proficiency for roles that demand robust file management capabilities.

1. How would you move a file from one directory to another in Linux?

To move a file from one directory to another in Linux, a candidate should explain that they would use the 'mv' command. This command allows users to move files or directories from one location to another.

For example, if you want to move a file named 'example.txt' from the 'Documents' directory to the 'Downloads' directory, the command would be 'mv Documents/example.txt Downloads/'.

Look for candidates to demonstrate a clear understanding of this command and to know that it can also be used to rename files. They should also be aware of potential issues such as overwriting existing files and how to handle them.

2. How do you copy a directory and its contents in Linux?

To copy a directory and its contents in Linux, candidates should mention the 'cp' command with the '-r' (recursive) option. This command allows the entire directory, including all its files and subdirectories, to be copied.

For instance, to copy a directory named 'Projects' to a new location called 'Backup', the command would be 'cp -r Projects/ Backup/'.

An ideal candidate response should include awareness of potential issues such as permission errors and how to ensure all files are copied accurately. They should also know how to use options like '-v' (verbose) to get detailed output of the copying process.

3. How would you delete a file in Linux?

To delete a file in Linux, candidates should explain the use of the 'rm' command. This command removes files or directories from the file system.

For example, to delete a file named 'example.txt', the command would be 'rm example.txt'.

Look for candidates who understand the importance of being cautious with this command, as it permanently deletes files. They should also know about using the '-i' option for interactive deletion, which prompts for confirmation before each file is deleted.

4. How do you create a new directory in Linux?

To create a new directory in Linux, the 'mkdir' command is used. This command allows users to create new directories within the file system.

For instance, to create a new directory named 'NewFolder', the command would be 'mkdir NewFolder'.

Ensure candidates also mention the '-p' option, which allows for creating parent directories as needed. This demonstrates their understanding of handling directory hierarchies efficiently.

5. How do you display the size of a directory and its contents in Linux?

To display the size of a directory and its contents in Linux, candidates should mention the 'du' command. This command provides disk usage information.

For example, to display the size of a directory named 'Documents', the command would be 'du -sh Documents/'. The '-s' option summarizes the total size, and the '-h' option makes the output human-readable.

Evaluate whether candidates understand the importance of these options for different use cases, such as quickly checking directory sizes or generating detailed reports for disk usage analysis.

6. How would you change the access permissions of a file in Linux?

To change the access permissions of a file in Linux, candidates should explain the use of the 'chmod' command. This command modifies the access permissions of files and directories.

For example, to make a file named 'example.txt' readable, writable, and executable by the owner, and readable by others, the command would be 'chmod 744 example.txt'.

Look for candidates who can interpret and explain permission notations (numeric and symbolic) and understand the significance of different permission levels for security and functionality.

7. How do you display the last few lines of a file in Linux?

To display the last few lines of a file in Linux, the 'tail' command is used. This command outputs the end of a file.

For example, to display the last 10 lines of a file named 'logfile.txt', the command would be 'tail logfile.txt'.

Candidates should also be familiar with options like '-n' to specify the number of lines to display. Assess their understanding of practical use cases, such as monitoring log files in real-time with the '-f' option.

8. How would you find files that were modified recently in Linux?

To find files that were modified recently in Linux, candidates should mention the 'find' command. This command searches for files and directories based on various criteria.

For example, to find files in the current directory that were modified in the last 7 days, the command would be 'find . -type f -mtime -7'.

An ideal response should include an understanding of different 'find' command options and how to combine them for precise searches. They should also demonstrate awareness of how this command can be integrated into larger scripts for automation purposes.

7 situational Linux Commands interview questions with answers for hiring top administrators

To determine whether your applicants have the practical skills and situational awareness needed for top Linux administrator roles, ask them some of these situational Linux commands interview questions. These questions are designed to reveal how candidates tackle real-world problems they might face on the job.

1. How would you troubleshoot a Linux system that has suddenly become unresponsive?

First, I would check the system logs for any error messages or unusual activity leading up to the unresponsiveness. Logs can be found in the /var/log directory, and files like syslog, dmesg, or specific application logs might provide clues.

Next, I would try to switch to a different virtual console using Ctrl+Alt+F3 (or another function key) to see if the issue is specific to the graphical interface or affects the entire system. If that works, it suggests the problem may be with the graphical environment rather than the underlying OS.

An ideal candidate should demonstrate a logical approach to troubleshooting, including checking logs, attempting to isolate the problem to specific system components, and using basic command-line tools to diagnose the issue.

2. Imagine you need to delete a user account immediately due to a security threat. What steps would you take?

First, I would use the 'who' or 'w' command to check if the user is currently logged in. If they are, I would use the 'pkill -KILL -u username' command to forcefully log them out and terminate any active processes they have running.

Next, I would delete the user account using the 'userdel' command, typically with the '-r' option to remove their home directory and mail spool. This ensures that all user-specific files are deleted.

Look for responses that show an understanding of both the urgency in handling security threats and the importance of cleaning up user data thoroughly. Candidates should also be aware of the potential risks and be prepared to handle them.

3. You notice that a server is running out of disk space. How would you approach this issue?

First, I would use the 'df -h' command to check disk usage and identify which partitions are filling up. This helps pinpoint where the problem lies.

Next, I would use 'du -sh /*' to see which directories are taking up the most space. From there, I could drill down into specific directories to identify large files or unnecessary data that can be removed.

Ideal candidates should mention steps like checking disk usage, identifying large files or directories, and taking appropriate action, such as cleaning up log files or old backups. They should also highlight the importance of monitoring and maintaining adequate disk space to prevent future issues.

4. A critical service has crashed on a server. What steps do you take to troubleshoot and resolve the issue?

First, I would use the 'systemctl status service-name' command to check the status of the service and look for any error messages or clues about why it might have crashed.

Next, I would review the service's log files, typically found in /var/log, to gather more details about the crash. Depending on the service, there might be specific logs that provide more insight.

A strong candidate will demonstrate a methodical approach to diagnosing service issues, including checking the service status, reviewing logs, and restarting the service if necessary. They should also discuss how they would prevent similar issues in the future, such as by setting up monitoring and alerts.

5. How do you handle a situation where a Linux server's network connectivity is down?

First, I would use the 'ping' command to check the connectivity to the local network and external sites to determine where the issue might be occurring. If pinging the default gateway fails, the problem is likely local.

Next, I would use the 'ip a' or 'ifconfig' command to check the network interfaces and ensure they are up and have the correct IP addresses. I would also verify the routing table using 'ip route' or 'route -n'.

Look for candidates who demonstrate a structured approach to diagnosing network issues, including checking connectivity, verifying network interface configurations, and examining routing tables. They should also mention potential follow-up steps, such as checking firewall rules or consulting with network administrators.

6. What steps would you take to secure a newly deployed Linux server?

First, I would ensure that all software packages are up-to-date by running 'apt-get update && apt-get upgrade' or the equivalent command for the server's package manager. This helps protect against known vulnerabilities.

Next, I would configure a firewall using tools like 'ufw' or 'iptables' to restrict access to only the necessary ports and services. Additionally, I would disable root login over SSH and set up key-based authentication.

Strong candidates should mention updating software, configuring firewalls, disabling unnecessary services, and setting up secure authentication methods. They should also discuss the importance of regular security audits and monitoring to maintain server security.

7. You need to automate a repetitive task on a Linux system. How would you go about it?

I would start by writing a shell script to perform the task. Shell scripting is powerful and allows for the automation of a wide range of tasks, from file management to system maintenance.

Next, I would use 'crontab' to schedule the script to run at regular intervals. This ensures the task is performed automatically without manual intervention.

Candidates should demonstrate an understanding of both scripting and scheduling tools available in Linux. They should also emphasize the importance of testing scripts thoroughly before deploying them in a production environment.

Which Linux Commands skills should you evaluate during the interview phase?

Assessing a candidate's proficiency with Linux commands in a single interview is challenging. However, there are key skills you should evaluate to ensure the candidate has a solid foundation in Linux command usage.

File Management

File management is a fundamental skill in Linux. It involves creating, deleting, moving, and managing files and directories, which are essential for system organization and script automation.

An assessment test can effectively gauge a candidate's understanding of file management. You can use our Linux online test which includes relevant MCQs.

You can also assess file management skills by asking targeted questions during the interview.

How would you recursively copy all .txt files from one directory to another?

Look for a candidate's understanding of the cp command with the -r option and appropriate usage of wildcards.

Process Management

Process management ensures that a candidate can handle and control active processes in a Linux environment. This includes starting, stopping, monitoring, and troubleshooting processes.

Using an assessment test with relevant MCQs can help identify a candidate’s competency in process management. Our Linux online test includes questions that cover this area.

To evaluate process management skills, consider asking direct, scenario-based questions during the interview.

How do you kill a process by its name rather than its PID?

Candidates should mention commands like pkill or killall, demonstrating their familiarity with process handling tools.

Permissions and Ownership

Understanding file permissions and ownership is critical for securing data and ensuring proper access control in a Linux system. This includes knowledge of chmod, chown, and chgrp commands.

An assessment with MCQs can effectively measure a candidate’s knowledge in this area. You might use our Linux online test for this purpose.

Asking specific questions about permissions and ownership can help you gauge a candidate's understanding during the interview.

How would you change the owner of a file to user 'john' and group to 'staff'?

Expect the candidate to explain the usage of chown john:staff filename and its implications.

Streamline Your Linux Talent Acquisition with Skills Tests and Targeted Interviews

When hiring for Linux expertise, it's important to verify candidates' skills accurately. This ensures you bring on board professionals who can handle your Linux-based systems and tasks effectively.

The most reliable way to assess Linux skills is through targeted skills tests. Consider using our Linux Online Test or Linux Bash Test to evaluate candidates' proficiency objectively.

After administering these tests, you can shortlist top performers for interviews. This two-step process helps you focus on candidates who have already demonstrated their Linux capabilities.

Ready to improve your Linux hiring process? Sign up for Adaface and access our range of IT skills assessments. For more information on our testing solutions, visit our IT Tests page.

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