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Linux Interview questions

Top 50 Linux Interview questions and answers for Beginners. Do you answer all?

1. What is Linux? How is it different from UNIX?

Linux is free open source multi-user operating system that is built on Linux kernel.The first version of Linux operating system was released on September 17, 1991, by Linus Torvalds.

Some Difference between Linux and Unix Operating System

LinuxUnix
Linux is open source anyone can use it free of costUNIX is copyrighted only big companies like IBM AIX and Sun Solaris and HP-UX use it
Linux is just a kernel.Unix is complete operating system
By default, Linux supports and use ext3 or ext4 file systemsUnix comes with jfs, gpfs (AIX), jfs, gpfs (HP-UX), jfs, gpfs (Solaris) filesystems
Redhat Enterprise Linux
Fedora Linux, Debian Linux, Suse Enterprise Linux, Ubuntu Linux are some popular Linux OS.
HP-UX, IBM AIX, Sun Solaris, Mac OS X are some Unix based operating systems
IRIX
Linux is considered as most user-friendly UNIX like operating systems.Apple OS X is most popular UNIX operating system for desktop usage.

2. Compare Linux with Windows?

Linux
1) Linux is opensource, the complete source code for Linux is available.
2) Linux is the GPL-licensed operating system, you are free to modify that software and use and even republish or sell it.
3) Download once and install it on as many PC you want.
4) Online peer support from the community via forums and online search.
Windows
1)  Source code for windows is not available.
2) You can modify or redistribute Window operating system.
3) In Windows, you are bounded to use one license in One PC only.If you have to install it on other PC you need another Licence.
4) Paid help desk support.

3. What is a kernel?

Kernal is the core of any operating system. Kernal acts as a middle man between computer hardware and operating system and controls everything on a computer.It is the first program that is loaded when a system starts.

4. What does uname command do?

<b>uname </b> is reporting command is Linux that is used to retrieve basic information about a computer’s hardware and software.

Synatax:  uname [options]

5. What does whoami do?

6. Please Explain LILO?

7. What is the difference between a and A?

8. What is the name and the UID of the administrator user?

9. What does ls -R do?

10. How to list all files, including hidden ones, in a directory?

11. What is LD_LIBRARY_PATH?

12. What are the Linux boot files?

13. What is grep command do?

14. What is difference between absolute and relative path?

15. What is Samba? Why is it used?

16. Please Provide Linux command to remove a directory with its contents?

17. Which command will show you free/used memory? Does free memory exist on Linux?

18. What is the difference between soft and hard mounting points?

19. What is SSH? How to connect to a remote server via SSH

20. How to tranfer a local file to a remote server in Linux

21. What is Virtual Memory?

22. List the basic components of Linux?

23. What is a shebang line?

24. How do you move files in Linux?

25. What does the command env do?

26. What does chmod +x FILENAMEdo?

27. How to add a new system user without login permissions?

28. What is CLI?

29. What is the difference between Telnet and SSH?

30. What does set -o do?

31. Difference between swap partition and swap file?

32. What does comm do and how to use it?

33. How to get the difference between two files in Linux?

34. How to add/remove a group from a user?

35. What is the full form of grep?

36. What is an A record, an NS record, a PTR record, a CNAME record, an MX record?

37. What does Sar provide? Where are Sar logs stored?

38. What is a zombie process?

39. What is a Split-Horizon DNS?

40. What is typical size for a swap partition under a Linux system?

41. What is an inode?

42. What is the difference between an environment and a local variable?

43. What is SSH port forwarding?

44. How can you list all hidden files in a directory?

45. What does the immutable bit do to a file?

46. How to create a link in Linux?

47. What does ps do?

48. Describe the mknod command and when you’d use it.

49. What are hard links?

50. What is “nohup” used for?

51. What is swap?

52. What is The SSL Handshake?

53. What is the TCP hand shake?