Preparing for a Linux interview requires a solid understanding of various concepts, commands, and system functionalities. Below is a curated list of essential Linux interview questions and answers to help you succeed:
1. What is Linux?
Linux is an open-source, Unix-like operating system based on the Linux kernel. It provides a free and customizable environment for users and developers, supporting a wide range of hardware platforms.
2. What are the key features of Linux?
- Open Source: Freely available and modifiable.
- Multitasking: Capable of running multiple programs simultaneously.
- Multiuser Capability: Allows multiple users to access system resources concurrently.
- Security: Offers robust security features, including user permissions and access controls.
- Portability: Can operate on various hardware platforms.
3. What is the Linux Kernel?
The Linux Kernel is the core component of the Linux operating system, managing system resources and facilitating communication between hardware and software components.
4. What is BASH?
BASH (Bourne Again Shell) is a command processor and scripting language for Unix/Linux systems, serving as the default shell for many Linux distributions.
5. What is the difference between Linux and Unix?
- Source Code: Linux is open-source; Unix is proprietary.
- Cost: Linux is generally free; Unix often requires licensing fees.
- Hardware Compatibility: Linux is highly portable; Unix is limited to specific hardware.
- User Base: Linux is widely used in personal computing; Unix is prevalent in enterprise environments.
6. What is a Shell in Linux?
A shell is a command-line interpreter that allows users to interact with the operating system by executing commands and running scripts.
7. What are the different types of Shells available in Linux?
- Bourne Shell (sh)
- C Shell (csh)
- Korn Shell (ksh)
- Bourne Again Shell (bash)
- Z Shell (zsh)
8. What is LILO?
LILO (Linux Loader) is a boot loader for Linux that manages the boot process of the operating system.
9. What is the significance of the 'root' account in Linux?
The 'root' account is the superuser with unrestricted access to all system commands and files, allowing for administrative tasks and system configurations.
10. What are file permissions in Linux?
File permissions determine the access level users have to files and directories, categorized into read (r), write (w), and execute (x) permissions for the owner, group, and others.
11. How do you change file permissions in Linux?
Use the chmod command followed by the permission settings and the file name. For example: chmod 755 filename
12. What is a symbolic link in Linux?
A symbolic link is a type of file that points to another file or directory, allowing for flexible file management.
13. How do you check disk usage in Linux?
Use the df command to report file system disk space usage and the du command to estimate file and directory space usage.
14. What is the purpose of the grep command?
The grep command searches for patterns within files, allowing users to filter and display specific lines that match the search criteria.
15. How do you view running processes in Linux?
Use the ps command to display currently running processes and the top command for a real-time view of system processes.
16. What is the difference between a process and a thread in Linux?
- Process: An independent program in execution with its own memory space.
- Thread: A lightweight sub-process sharing the same memory space as its parent process.
17. How do you terminate a process in Linux?
Use the kill command followed by the process ID (PID). For example: kill 1234
18. What is a daemon in Linux?
A daemon is a background process that runs continuously, typically waiting to handle service requests.
19. How do you schedule tasks in Linux?
Use the cron daemon to schedule recurring tasks and the at command for one-time tasks.
20. What is the purpose of the /etc/passwd file?
The /etc/passwd file stores user account information, including usernames, user IDs, group IDs, home directories, and login shells.
21. How do you create a new user in Linux?
Use the useradd command followed by the username. For example: useradd newuser
22. What is the difference between su and sudo?
su: Switches to the superuser account or another user account, requiring the target account's password.sudo: Executes a single command with superuser privileges, requiring the current user's password and proper authorization.
23. How do you check the Linux kernel version?
Use the uname -r command to display the kernel version.
24. What is a package manager in Linux?
A package manager is a tool that automates the installation, updating, and removal of software packages. Examples include apt for Debian-based systems and yum for Red Hat-based systems.
25. How do you update installed packages in Linux?
- For Debian-based systems:
sudo apt update && sudo apt upgrade - For Red Hat-based systems:
sudo yum update
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