The Linux operating system is one of the fastest and most powerful. Consequently, the Linux OS is extremely popular, so many positions are open for Linux professionals. Although demand is high, you still need to ace that Linux-related job interview, and that’s why we’re here.
This article provides a comprehensive set of Linux interview questions and answers for the aspiring candidate. We break down the questions into skill levels, admins, and Linux commands and round out the article with a UI/UX learning opportunity.
So, let’s dive head-first into some Linux interview questions and answers for rookies and work our way up.
Linux Interview Questions for Beginners
Q: How would you explain Linux to someone who’s never heard of it?
- A: Linux is an open-source operating system based on the Linux kernel. It can run on different platforms, providing a cost-effective, user-friendly OS that allows programmers to create and modify source code variations. Linux is known for its stability, security, and versatility.
Q: What’s the difference between Linux and Unix?
- A: Linux is free, uses a graphic user interface with an optional command line interface, is portable, and is used on home-based computers, phones, etc. On the other hand, Unix offers different paid structures for different levels, uses a command line interface, is not portable, and is used in server systems and mainframes.
Q: What is a CLI?
- A: CLI stands for Command language Interpreter, and it interacts with computer programs, where users issue commands in the form of text lines. CLI also interacts with computer terminals; the interface accepts text lines and changes them into a command to the operating system.
Q: Name some of Linux’s benefits.
- A: Linux’s benefits include:
- It’s open source, so it’s free and readily available.
- It’s robust and adaptable, able to operate for prolonged periods without crashing, and strongly immune to security threats.
- It’s more secure, providing security using authentication features such as password authentication, file system access control, and security auditing.
- It can run more than one function or an application simultaneously.
- Linux has its own software repository.
- It supports customized keywords and multiple language keyboards.
- It provides a GUI interface for users to interact with the system and accommodates GUI applications like VLC, Firefox, etc.
Q: What is Bash?
- A: Bash is a Unix shell and command processor created by Brian Fox for the GNU project. It’s free software that acts as a replacement for the Bourne Shell. Bash is an interpreted process, not compiled, and can run in the terminal window. This process lets users write commands and initiate actions. In addition, Bash can read commands from shell scripts.
Q: Bash isn’t the only shell. List the standard Linux shell types.
- A: Common Linux shells include:
- Bash (Bourne Again Shell)
- Sh (Bourne Shell)
- Csh (C Shell)
- Ksh (Korn Shell)
- Zsh (Z Shell)
- Fish (Friendly Interactive Shell)
Q: What is LILO, and why is it used?
- A: LILO is short for Linux Loader and is a Linux Boot Loader that loads the Linux OS into the main memory to commence execution. Most computers only come with bootloaders for Windows or Mac OS. So, users who want the Linux OS must install a special boot loader such as LILO. When the computer is powered up, BIOS runs initial tests and transfers the control to the Master Boot Record. This stage is when LILO loads the Linux OS and starts it. LILO’s advantage is that it allows a faster boot of the Linux OS.
Q: What are the two kinds of Linux User Modes?
- A: User Mode is the default mode for running user-level applications, processes, and programs. User Mode offers isolation and protection that prevents user-level processes from interfering with essential system operations. On the other hand, Kernel Mode, also known as Privileged or Supervisor Mode, executes the operating system’s kernel. This mode gives the kernel access to the system and hardware resources. It can execute privileged instructions and perform critical tasks like handling interrupts, managing memory, and controlling hardware devices.
Q: What is the root account?
- A: A root account is like a system administrator account. It provides complete system control and allows users to create and maintain user accounts, assign different permissions for each account, and perform related tasks.
Q: What is the maximum file name length under Linux?
- A: File names cannot exceed 255 bytes.
Q: What is a swap space?
- A: Swap spaces are used as an extension of RAM. Its primary function is substituting disk space for RAM when the actual RAM lacks enough space to hold all the executing programs, and more space is needed.
Linux Interview Questions for Experienced Professionals
Now, let’s check out a handful of Linux interview questions for experienced professionals.
Q: What’s a virtual desktop?
- A: A virtual desktop is an alternative to minimizing and maximizing windows on the current desktop. The virtual desktop lets you open one or more programs on a clean slate instead of minimizing or restoring the needed programs.
Q: What are Linux’s three file permissions?
- A: The three file permissions are:
- Read. Reads the file and lists the directory.
- Write. Writes new files in the directory.
- Execute. Accesses and runs the file in a directory.
Q: List some Linux distros (distributors) and why they’re used.
- A: Here are five important distros:
- Linux Mint. A stable, robust distro that uses Mate Desktop and Cinnamon.
- Debian. A user-friendly, robust, stable, and well-oiled release cycle.
- Ubuntu. It’s available for both server and desktop editions.
- openSUSE. It suits new and existing users and is well-suited for UI UX design.
- Manjaro. It’s ideal for new and experienced users.
Q: Describe Linux’s architecture and basic components.
- A: Linux is made up of the following elements:
- Kernel. The Kernel is Linux’s main part or core of Linux and is typically responsible for all major OS activities such as process management, device management, etc.
- GUI. The Graphic User Interface allows users to interact with the system.
- System Utility. These programs are responsible for performing specialized and individual-level tasks.
- Application Programs. Functions designed to perform specific tasks.
- System Library. This element consists of special functions or programs that help the application programs or system utilities access kernel features without requiring code. It is used to implement OS functionality.
- Shell. The shell is an environment where users run commands, scripts, and programs. The shell is an interface between the user and kernel, hiding all kernel function complexities from the user.
- Hardware. This element covers the physical devices, including the mouse, keyboard, display, CPU, etc.
Q: What’s the difference between internal and external commands?
- A: Internal commands are run directly by the shell, and there’s no separate process to run the commands. The kernel runs external commands, and every command has its own unique process id.
Q: Explain the differences between DOS and Bash.
- A: Bash commands are case-sensitive and don’t follow a file naming convention, while DOS commands aren’t case-sensitive and follow file naming conventions.
Q: What’s the first process started by the kernel in Linux, and what’s the process id?
- A: The first process is “init,” and its process id is 1.
Linux Admin Interview Questions
Here’s a sample of a half-dozen popular Linux admin interview questions and answers.
Q: Why do you need LVM?
- A: LVM stands for Large Volume Management. It’s a storage management device that lets users create, resize, and delete LVM partitions. LVM increases abstraction, flexibility, and control, collects existing storage devices into a group, and allocates logical units.
Q: What is network bonding?
- A: Network bonding combines more than two network interfaces to create a single network interface. Network bonding offers performance improvement and redundancy by boosting network bandwidth and throughput.
Q: Where are kernel modules located?
- A: They are found in lib/modules/kernel-version/. This directory stores all the information about compiled drives under the Linux system.
Q: How do you change the default run level?
- A: Use the <init> command.
Q: How do you lock a user account for security purposes?
- A: Here are three ways to do it:
- Lock or disable the password using <passwd>
- Expire the user’s account using <usermod> or <chage>
- Change the shell with the nologin command </sbin/nologin>
Q: List the default ports for SMTP, DNS, FTP, DHCP, SSH, and squid.
- A: The default ports are:
- SMTP: 25
- DNS: 53
- FTP: 20(Data Transfer) 21(Connections Established)
- DHCP: 68(dhcp client), 67(DHCP server)
- SSH: 22
- Squid: 3128
Linux Commands Interview Questions
Here are ten Linux commands interview questions and answers.
Q: What are user management’s basic commands?
- A: The basic commands are:
- chage
- chmod
- chown
- chsh
- last
- lsof
- newusers
- useradd
- userdel
Q: What command uncompresses gzip files?
- A: Use the <gunzip> command to uncompress these files.
Q: How do you create a new file or modify an existing file in Linux?
- A: Use the command <vi filename>.
Q: How do you check and verify the status of the bond interface?
- A: Use the command < cat /proc/net/bonding/bond0>.
Q: What are the primary Linux directory commands?
- A: The directory commands are:
- pwd: <$ pwd > Displays the present working directory’s path
- ls: <$ ls> Lists all files and directories in the present working directory
- cd: <$ cd> <path to new directory> Changes the present working directory
- mkdir: <$ mkdir> <name (and path if required) of new directory> Creates a new directory
- rmdir: <$ rmdir> <name (and path if required) of directory> Deletes a directory
Q: What is the grep command?
- A: Grep stands for Global Regular Expression Print and searches for text in a file by pattern matching based on a regular expression.
Q: What are Linux’s process states?
- A: The process states are:
- Ready. The process is created and ready to run
- Running. The process is being executed
- Blocked. Also called Wait; the process is waiting for user input
- Terminated or completed. The process completed execution or was terminated by the OS
- Zombie. The process is terminated, but the information is still in the process table
Q: What are daemons?
- A: Daemons are computer programs that run as a background process to provide functions that may otherwise not be available in the base OS. Daemons are typically used to run services in the background without interactive users directly controlling them. Daemons handle periodic requests and then forward these requests to the appropriate programs for execution.
Q: When do you use the tar command?
- A: You extract or create an archived file using the tar command.
Q: What is the netstat command?
- A: The netstat command gives information about the network and routing tables, interface statics, and additional system information.
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