50 Linux System Admin Questions and Answers

Linux System Administration

1. What does nslookup do?

nslookup is a network administration command-line tool available for many computer operating systems for querying the Domain Name System (DNS) to obtain domain name or IP address mapping or for any other specific DNS record.

2. How do you display the top most process utilizing CPU process?

top will display what is using your CPU.
ps -eo pcpu,pid,user,args | sort -k1 -r | head -10 will also display the top 10 processes

3. How to check all open ports on a Linux machine and block the unused ports?

netstat -t(tcp)
netstat -u(udp)or
netstat -tulpn
to verfy the open ports
to block u have to use iptable & tcp_wrappers( hosts.deny
file)

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

5. Explain the boot process of Unix System in details.

6. How do you change the permissions? How to create a file that’s read-only property?

7. Explain SUDO in detail. What are its disadvantages?

8. What is the difference between UDP and TCP?

9. Describe the boot order of a Linux machine.

10. Design a 3-tier web application.

11. Sketch how you would route network traffic from the internet into a few subnets.

12. How do you know about virtualization? Is it good to use?

13. What are different levels of RAID and what level will you use for a web server and database server?

14. List some latest developments in open source technologies.

15. Have you ever contributed to an open source project?

16. Systems engineer or a systems administrator? Explain?

17. List some of the common unethical practices followed by a system professional.

18. What is the common size for a swap partition under a Linux system?

19. What does a nameless directory represent in a Linux system?

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

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

22. Explain a hardlink. What happens when a hardlink is removed?

23. What happens when a sysadmin executes this command: chmod 444 chmod

24. How do you determine the private and public IP addresses of a Linux system?

25. How do you send a mail attachment using bash?

26. Tell me something about the Linux distros used on servers.

27. Explain the process to re-install Grub in Linux in the shortest manner.

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

29. What is a zombie process? State its causes?

30. When do we prefer a script over a compiled program?

31. How to create a simple master/slave cluster?

32. What happens when you delete the source to a symlink?

33. How to restrict an IP so that it may not use the FTP Server?

34. Explain the directory structure of Linux. What contents go in /usr/local?

35. What is git? Explain its structure and working.

36. How would you send an automated email to 100 people at 12:00 AM?

37. Tell me about ZFS file system.

38. How to change the default run level in a Linux system?

39. How would you change the kernel parameters in Linux?

40. State the differences between SSH and Telnet.

41. How would you virtualize a physical Linux machine?

42. Tell me about some quirky Linux commands.

43. Explain how HTTPS works.

44. Do you know about TOR browser? Explain its working.

45. How to trigger a forced system check the next time you boot your machine?

46. What backup techniques do you prefer?

47. Tell me something about SWAP partition.

48. Explain Ping of Death attack.

49. How do you sniff the contents of an IP packet?

50. Which OSI layer is responsible for making sure that the packet reaches its correct destination?

The Answers will be updated soon