Do you know that we can ease your tense life a bit with our amazing accumulated Linux System Administrator Interview Questions and Answers for your future interview? If not, then your time has come.

Here, we will answer the most commonly searched and asked questions in the interview for a vacant seat for a Linux System Administrator. What are we waiting for? Let’s get into it now!

What is Linux Administration?

The specialized activity of configuring, overseeing, and maintaining servers and computer systems running the Linux operating system to guarantee optimal security and uptime is known as Linux administration.

What is Linux Administration?

It entails fundamental duties like installing software, setting up network services, and managing user accounts while keeping an eye on system performance to avoid bottlenecks. Administrators also carry out crucial maintenance duties, such as applying security patches, backing up data, and creating shell scripts to automate tedious system activities.

Let’s take a look at the Linux System Administrator Interview Questions and Answers and see how you can crack the interview with ease!

Top 30 Linux System Administrator Interview Questions and Answers

1. What is the Linux boot process?

The Linux boot process is a multi-step procedure that uses BIOS/UEFI to activate hardware, transfers control to a bootloader such as GRUB to load the kernel into memory, and then launches the init or systemd process to launch all required system services and user interfaces.

2. Difference between a hard link and a soft link in Linux?

A soft link, also known as a symbolic link, is just a shortcut that points to the filename and becomes broken or "dangling" if the original file is moved or removed. In contrast, a hard link is a direct reference to a file's data on the disk, sharing the same inode, meaning it remains valid even if the original filename is deleted.

3. How does file permission work in Linux?

Linux file permissions are controlled by the chmod command using either symbolic characters or octal numeric values. They use a set of nine bits arranged into three triplets to determine Read (r), Write (w), and Execute (x) access for the Owner, Group, and Others.

4. What is the difference between chmod, chown, and chgrp?

The basis of Linux file security is formed by chown, which alters the file's user ownership, chgrp, which explicitly modifies the group ownership, and chmod, which modifies the access rights (Read, Write, Execute) of a file or directory.

5. How to check disk space and inode usage in Linux?

Use the command df -h to get a human-readable overview of the filesystem capacity and df -i to view the total, used, and free index nodes for each mounted partition.

6. What is LVM, and why is it used?

A layer of abstraction over physical hard drives is created by LVM (Logical Volume Manager), a storage management solution that enables you to combine several disks into a single "Volume Group" and build "Logical Volumes" that may be dynamically resized, moved, or snapshotted without causing system outages.

7. How to find and kill a process in Linux?

In Linux, you can use pgrep process_name or ps aux | grep process_name to discover a process's unique Process ID (PID) and then terminate it by typing kill PID. Alternatively, you can use pkill process_name to find and kill a process in a single step based on its name.

8. Difference between systemctl and service commands?

The service command is a legacy high-level wrapper that was initially used for SysVinit but now mainly serves as a compatibility layer that reroutes your requests to systemctl on modern distributions, whereas systemctl is the contemporary, potent command-line tool created especially for the systemd init system to manage services, units, and dependencies.

9. What is cron, and how does it work?

In Unix-like operating systems, Cron is a time-based task scheduler that employs a background service called the cron daemon (crond) to automatically run commands or scripts at predetermined intervals specified by a five-field syntax in a configuration file called a crontab.

10. How to check memory and CPU usage in Linux?

The top or htop programs provide a real-time interactive dashboard of all system resources; the free -h command provides a brief picture of available RAM; and mpstat provides a comprehensive breakdown of processor activity.

11. What is SELinux, and how do you disable or configure it?

A kernel security module called SELinux (Security-Enhanced Linux) offers a way to support access control security policies through Mandatory Access Control (MAC). You can either permanently disable it by setting SELINUX=disabled in the /etc/selinux/config file, followed by a system reboot, or temporarily toggle it using setenforce 0 (Permissive) or setenforce 1 (Enforcing).

12. Difference between ext4 and xfs file systems?

While XFS is a high-performance, 64-bit filesystem intended for huge scalability and parallel I/O, it cannot be shrunk once created. In contrast, Ext4 is a tried-and-true general-purpose filesystem that allows both expanding and shrinking partitions and performs well with fewer files.

13. How to troubleshoot a Linux server that is running slowly?

Use the top or htop programs to find CPU and RAM bottlenecks, iostat to look for disk I/O congestion, and nload or iftop to find network saturation while troubleshooting a slow Linux server.

14. What is swap memory, and how to increase it?

When your actual RAM is full, the operating system can temporarily unload idle data by using swap memory, a special section of your hard drive or SSD that functions as an extension of your physical RAM. You can use fallocate -l [size]G /swapfile to create a new swap file, chmod 600 to set secure rights, mkswap to format it, then swapon to activate it.

15. How does SSH work, and how do you secure it?

SSH can be protected by turning off root logins, altering the default port (22), and using SSH key-based authentication rather than passwords. SSH operates by creating an encrypted tunnel between a client and a server using a "handshake" to negotiate session keys and verify host identification.

16. Difference between rpm and yum/dnf?

YUM and its quicker successor DNF are high-level "front-ends" that automatically search repositories, download necessary files, and resolve all dependencies for you, whereas RPM is a low-level tool that installs individual .rpm files, but fails if dependencies are missing.

17. What is a zombie process in Linux?

A zombie process, also known as a dead process, is a terminated child process that stays in the system's process table because its parent has not yet used the wait() system function to check its exit status. As a result, it occupies a Process ID (PID) without using any CPU or RAM.

18. How to configure network settings in Linux?

In Linux, you can manage NetworkManager connections on desktops with nmcli or nmtui, modify YAML files in /etc/netplan/ (Ubuntu/Debian) or key-value files in /etc/sysconfig/network-scripts/ (RHEL/CentOS) for long-term configurations, or use the ip command for temporary changes.

19. How to check open ports in Linux?

Use the more recent ss -tulpn command or the older netstat -tulpn command to list all TCP and UDP sockets that are listening, together with the Process IDs (PIDs) and service names that correspond to them, to verify open ports on Linux.

20. What is RAID, and explain RAID levels?

Depending on the particular "level" selected, RAID (Redundant Array of Independent Disks) is a storage virtualization technology that combines several physical hard drives into a single logical unit to enhance performance, offer data redundancy, or both.

21. How to manage users and groups in Linux?

User and group management in Linux is primarily handled through specialized command-line utilities such as useradd, usermod, and groupadd, which update the system's central identity databases located in the /etc/passwd, /etc/shadow, and /etc/group files.

22. How to check and analyze log files in Linux?

In Linux, you can use journalctl to query the structured systemd journal for particular services or timeframes, grep to look for specific fault patterns, and tail -f to watch real-time changes.

23. What is the purpose of the /proc file system?

A "pseudo-filesystem" that serves as a real-time link between the Linux kernel and user space, the /proc file system offers a hierarchical interface for accessing core kernel data structures, keeping an eye on hardware, and instantly seeing or changing process information.

24. How to mount and unmount file systems?

To mount a file system, attach a partition to an existing directory using sudo mount /dev/device_name /mount_point. To safely detach the partition, use sudo umount /mount_point (take care of the single "n" in "umount") to make sure all outstanding data is written to the disk.

25. Difference between tar, gzip, and zip?

While gzip is a "compressor" that shrinks individual files (usually a tarball to create a.tar.gz), tar is a "archiver" that bundles multiple files into a single "tarball" without reducing their size, and zip is an all-in-one tool that both archives and compresses files, though it is less effective at maintaining Linux-specific file permissions than the tar/gzip combo.

26. How to troubleshoot disk space issues in Linux?

Use df -h to find the entire partition and then du -ah / | sort -rh | head -n 20 to determine the top 20 largest files or directories using that space to fix disk space issues in Linux.

27. What are runlevels or systemd targets?

The SysV init system uses runlevels, which are legacy numeric states (0–6), to specify which services launch at boot. Systemd targets, on the other hand, are their contemporary, named replacements (such as multi-user.target), which represent system states using a flexible dependency-based model instead of rigid sequences.

28. How to secure a Linux server?

In the following ways, you can secure a Linux server:

a) Harden SSH Access,

b) Enable a Firewall,

c) Implement the Principle of Least Privilege,

d) Automate Security Updates, and

e) Install Intrusion Prevention Tools.

29. How to recover the root password in Linux?

In the following ways, you can recover the root password in Linux:

a) Interrupt Boot,

b) Edit Kernel Line,

c) Boot to Shell,

d) Reset Password, and

e) Reboot.

30. What are common Linux troubleshooting commands?

The following are common Linux troubleshooting commands:

a) System Resources (top / htop),

b) Disk Space and I/O (df / iostat),

c) Log Analysis (journalctl / dmesg),

d) Network Connectivity (ss / ip), and

e) Process Health (ps / systemctl).

Conclusion

Now that we have talked about the Linux System Administrator Interview Questions and Answers, you might want to take the interview quickly and crack it with ease. However, for those who have just entered the world of the IT Industry and want to work with a powerful Operating System, can go with the Best Linux Essential Training Course in New Delhi offered by Craw Security to IT Aspirants.

During the training sessions, students will be able to use their knowledge on various tasks assigned by the professionals to them to get a real-time experience. What are you waiting for? Contact, Now!

Top 30 Linux System Administrator Interview Questions and Answers

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