LINUX Interview questions and Answers

LINUX COMMANDS

1. What is Linux?
Linux is an open-source operating system / kernel that forms the basis for various Linux distributions.

2. What are the main components of a Linux system?
The main components of a Linux system are the kernel, shell, and file system.

3. What is the role of the Linux kernel?
The Linux kernel is the core component of the operating system that manages system resources and provides services to applications.

4. What is a shell in Linux?
The shell is a command-line interpreter that allows users to interact with the operating system.

It accepts and executes commands.

5. What are some popular Linux distributions?
Popular Linux distributions include Ubuntu, Debian, Fedora, CentOS, and Red Hat Enterprise Linux.

6. How do you change file permissions in Linux?
The "chmod" command is used to change file permissions in Linux.
For example, "chmod 755 filename" sets read, write, and execute permissions for the owner and read and execute permissions for others.

7. What is the purpose of the "grep" command?
The "grep" command is used to search for specific patterns within files.
It is often used for text searching and filtering.

8. How do you find files in Linux?
The "find" command is used to search for files and directories in Linux based on various criteria like name, size, and permissions.

9. What is the purpose of the "top" command?
The "top" command is used to monitor system processes and resource usage in real-time.

10. How do you check the disk usage in Linux?
The "df" command is used to display disk space usage of file systems.

11. What is a symbolic link in Linux?
A symbolic link, also known as a soft link, is a special type of file that points to another file or directory.

12. What is the purpose of the "tar" command?
The "tar" command is used to create and manipulate archive files, often used for bundling multiple files into a single file.

13. How do you start and stop services in Linux?
Service management varies among distributions. In systemd-based systems, you can use commands like "systemctl start service_name" and "systemctl stop service_name" to start and stop services.


14. What is the purpose of the "ping" command?
The "ping" command is used to check the connectivity between a source and a destination using Internet Control Message Protocol (ICMP) echo requests and replies.

15. How do you check the network configuration in Linux?
The "ifconfig" command is used to display the network configuration of a Linux system. However, in newer distributions, it has been replaced by the "ip" command.

16. What is SSH and how does it work?
SSH (Secure Shell) is a cryptographic network protocol used for secure remote login, command execution, and file transfer between computers. It encrypts the communication between the client and server.

17. How do you kill a process in Linux?
The "kill" command is used to terminate a process. You can use the process ID (PID) or the "killall" command to kill processes by name.

18. What is the purpose of the "rsync" command?
The "rsync" command is used for efficient file synchronization and transfer between systems.

19. How do you check system hardware information in Linux?
The "lshw" command can be used to obtain detailed information about the hardware of a Linux system.

20. What is a firewall in Linux?
A firewall is
a security mechanism that controls incoming and outgoing network traffic based on a set of rules. It helps protect the system from unauthorized access.

21. How do you check the system's IP address in Linux?
The "ip addr" command is used to display the IP addresses assigned to network interfaces on a Linux system.
22. What is the purpose of the "cron" daemon?
The "cron" daemon is used for scheduling and automating recurring tasks in Linux.

23. How do you mount a filesystem in Linux?
The "mount" command is used to attach a filesystem to the directory tree.

24. What is the purpose of the "chroot" command?
The "chroot" command is used to change the root directory for a process, creating a separate environment with its own root directory.

25. How do you compress and decompress files in Linux?
The "gzip" and "gunzip" commands are used to compress and decompress files using the gzip compression algorithm.

26. What is the purpose of the "iptables" command?
The "iptables" command is used for configuring the Linux kernel firewall, which filters network traffic based on user-defined rules.

27. How do you check the CPU usage in Linux?
The "top" command or tools like "htop" and "mpstat" can be used to monitor CPU usage in Linux.

28. What is the purpose of the "useradd" command?
The "useradd" command is used to create user accounts in Linux.

29. How do you search for a string within files in a directory?
The "grep" command with the "-r" option can be used to search for a string recursively within files in a directory.