10 Core Linux Interview Questions with Answers

Linux is a widely used open-source operating system that has become increasingly popular over the years. As a result, there is a high demand for Linux professionals, and many companies are looking for qualified candidates who have the right knowledge and experience. If you are looking to get into a Linux-related career, then it's important to prepare yourself for interviews with some of the most common Linux-related questions that you may face. In this article, we will discuss some of the core Linux interview questions with answers that you can use to prepare for your next interview.

What is Linux, and What is it Used For?

Linux is an open-source operating system based on the Unix operating system. It was created by Linus Torvalds in 1991 and is used for a variety of purposes, including server management, desktop computing, and mobile devices. The operating system is highly customizable and can be adapted to a wide range of applications, making it a popular choice for businesses and individuals alike.

What are the different types of Linux distributions, and what are their differences?

There are several different types of Linux distributions, each with their own unique features and benefits. Some of the most popular distributions include −

• Ubuntu − Ubuntu is one of the most popular Linux distributions and is known for its ease of use and strong community support.

• Debian − Debian is a stable and reliable distribution that is known for its security and stability.

• Red Hat Enterprise Linux (RHEL) − RHEL is a commercial distribution that is widely used in enterprise environments.

• Fedora − Fedora is a community-driven distribution that is known for its cutting-edge features and frequent updates.

• CentOS − CentOS is a free, community-driven distribution that is based on RHEL.

Each distribution has its own set of features and benefits, so it's important to choose the one that best suits your needs and requirements.

What is the root user, and why is it important?

The root user is the administrative user in Linux and has complete control over the system. This user can perform any task on the system, including installing software, creating and deleting users, and changing system settings. It's important to note that the root user should only be used when necessary and should not be used for everyday tasks, as it can be dangerous and can cause system instability.

What is a shell, and what are the different types of shells available in Linux?

A shell is a command-line interface that allows users to interact with the operating system. There are several different types of shells available in Linux, including −

• Bash (Bourne-Again SHell) − Bash is the most popular shell in Linux and is used by default in most distributions.

• Zsh (Z SHell) − Zsh is a powerful shell that is highly customizable and has several advanced features.

• Fish (Friendly Interactive SHell) − Fish is a user-friendly shell that has a modern and intuitive interface.

• Ksh (Korn SHell) − Ksh is a powerful shell that is compatible with Bash and has several advanced features.

What is a package manager, and why is it important?

A package manager is a tool that is used to manage software packages in Linux. It allows users to easily install, update, and remove software packages from the system. Some of the most popular package managers in Linux include −

• Apt (Advanced Package Tool) − Apt is used in Debian and Ubuntu distributions and is known for its ease of use and strong community support.

• Yum (Yellowdog Updater, Modified) − Yum is used in Red Hat and CentOS distributions and is known for its powerful dependency management system.

• Pacman − Pacman is used in Arch Linux and is known for its fast and efficient package management system.

Having a good understanding of package managers is important for maintaining a stable and secure Linux system, as it allows for easy management of software packages and ensures that the system is up-to-date with the latest security patches and updates.

What is a file system, and what are the different types of file systems available in Linux?

A file system is a method used to organize and store files on a storage device. Linux supports several different file systems, including −

• Ext4 − Ext4 is the default file system used in most Linux distributions and is known for its stability and reliability.

• Btrfs (B-Tree File System) − Btrfs is a modern file system that supports advanced features such as snapshotting and data deduplication.

• XFS (Extended File System) − XFS is a high-performance file system that is optimized for large files and is commonly used in enterprise environments.

• NTFS (New Technology File System) − NTFS is a file system used by Windows operating systems and is supported in Linux through third-party drivers.

What is a firewall, and why is it important in Linux?

A firewall is a network security system that is used to monitor and control incoming and outgoing network traffic. In Linux, firewalls are typically managed using the iptables or nftables tools. A firewall is important in Linux because it helps to protect the system from unauthorized access and attacks, and ensures that only authorized traffic is allowed to pass through the network.

What is SSH, and how is it used in Linux?

SSH (Secure Shell) is a network protocol that is used to securely connect to remote servers and devices. It allows users to securely access and manage remote systems from a local machine. SSH is commonly used in Linux for remote administration and is often used to access servers in data centers or cloud environments.

What is RAID, and how is it used in Linux?

RAID (Redundant Array of Independent Disks) is a data storage technology that uses multiple disks to improve data reliability and performance. RAID is commonly used in Linux for file servers and other data-intensive applications. There are several different types of RAID, including RAID 0, RAID 1, RAID 5, and RAID 6, each with their own set of benefits and drawbacks.

What is SELinux, and how is it used in Linux?

SELinux (Security-Enhanced Linux) is a security framework that provides mandatory access control (MAC) in Linux. It is used to control access to system resources and to prevent unauthorized access to sensitive data. SELinux is commonly used in Linux-based systems that require a high level of security, such as government and military systems.

What is a kernel, and why is it important in Linux?

The kernel is the core component of the Linux operating system and is responsible for managing system resources and providing access to hardware devices. It is the interface between the hardware and the software and is responsible for managing tasks such as memory management, process scheduling, and input/output operations. The kernel is one of the most important components of Linux and is responsible for the stability and reliability of the system.

What is a process, and how is it managed in Linux?

A process is a running instance of a program in Linux. It is managed by the kernel and is assigned a unique process ID (PID) that can be used to identify and manage the process. Processes can be started, stopped, and managed using various Linux tools, such as the ps and kill commands.

What is a cron job, and how is it used in Linux?

A cron job is a scheduled task that is run automatically at specified intervals in Linux. It is commonly used for tasks such as system backups, database maintenance, and log file rotation. Cron jobs are managed using the crontab command and can be scheduled to run at any interval, from every minute to once a year.