Learn The Basic Linux Commands With This Awesome Cheat Sheet

 
Fox solutions: Here I’m sharing a useful Linux commands cheat sheet that you can print and keep it as a learning guide or a refresher. The cheat sheet is organized according to different commands and sections for easy use.

If you are willing to become a system administrator or trying to make a shift from Windows to Linux, you need to become well-versed with basic Linux commands.

Even if you adopted Linux a long time ago, it becomes difficult to remember all the commands and use them to perform powerful tasks with just a few keystrokes. In such times, you feel the need of an ultimate cheat sheet that could act as an answer to all your problems.

Recently, I came across a basic Linux commands cheat sheet that one could easily use as a refresher or a learning guide.
This cheat sheet organizes all the commands in 13 different sections according to their usage to help you out with the information on package installation, how to call up system info, or how to manipulate a file.
Prepared by LinOxide, you can go ahead and download the cheat sheet in PDF format and take a look at a more detailed reference guide.

Below is the image that you can save and print:

 

Top 50 Linux System Administrator Interview Questions

Fox Solutions: Today, the job opportunities for Linux experts are more than ever. The Linux SysAdmin interview questions range from basic Linux questions to networking, DevOps, and MySQL questions. So, one needs to prepare adequately to ensure success in the Linux system administrator interview process. 


According to a report, the open source and Linux job market is full of new opportunities. Due to the increasing adoption of open source technologies by the technology giants (Microsoft says HELLO!), there are ample job opportunities for system administrators and DevOps professionals.

While a huge demand continues to exist, just like any other job in the technology world, SysAdmins have to go through a rigorous hiring process that consists of preparing a professional resume, technical exams, and interview questions. Out of these, cracking a job interview is often the most critical test.
During an interview, a candidate’s personal qualities are also checked and it’s evaluated if he/she is a right fit for the company. Apart from being calm and composed, being well-prepared for an interview is the best thing one can do in order to crack a Linux SysAdmin interview.

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If you open your web browser and search for the phrase Linux SysAdmin interview questions, you’ll get a long list of search results that will help your practice. Apart from the straightforward conceptual questions like “What does the permission 0750 on a file mean?”, Linux SysAdmin interviews also come loaded with expert questions like “How do you catch a Linux signal on a script?”
To help you out in the Linux system administrator  interviews, I’ve compiled a list of my favorite questions of variable difficulty. These questions are framed with different approaches to find out more about the candidate and test his/her problem-solving skills:

1. What does nslookup do?

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

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

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?

Linux Filesystems Explained — EXT2/3/4, XFS, Btrfs, ZFS

 

Fox Solutions: Linux is known for supporting the most filesystems out of all operating systems. There are many retro ones, there are the tried and true, and then there are the next generation filesystems with amazing features. There are so many, in fact, that it can be extremely daunting to the average user.
 
 The first time I installed Ubuntu on my computer, when I was sixteen, I was astonished by the number of filesystems that were available for the system installation. There were so many that I was left overwhelmed and confused. I was worried that if I picked the wrong one my system might run too slow or that it might be more problematic than another. I wanted to know which was the best.
Since then, things have changed quite a bit. Many Linux distributions offer a ‘standard’ filesystem that an installation will default to unless otherwise specified. I think this was a very good move because it assists newcomers in making a decision and being comfortable with it. But, for those that are still unsure of some of the contemporary offerings, we’ll be going through them today.

EXT2/3/4:

Extended Filesystem is by far the most popular filesystem among Linux desktop installations. It has been tried and tested, it is no doubt a solid and stable filesystem. It supports all of the standard features of the Linux kernel like quotas, POSIX attributes, and ACLs, so it still a viable solution for a desktop or server. However, there are no plans to create a new iteration of the EXT4 filesystem. The authors have decided to let it go praising Btrfs as the next defacto for Linux.

XFS:

XFS is the recommended solution for Red Hat Enterprise Linux since release 7. It has a rich history in supercomputing and server use dating back to its introduction in IRIX OS in 1994, which is probably part of why Red Hat is advocating its use. There are, however, some key disadvantages to using XFS. The most notable of the disadvantages is the lack of data checksums or ECC leaving it susceptible to silent data corruption, otherwise known as “bit rot,” making the lack of transparent compression, the ability to shrink a volume, or the inability to snapshot the volume without external tools and freezing I/O the least of your concerns.
Despite these shortcomings, XFS is known for being very stable and very fast due to its optimized parallel I/O, and if you can compensate for the demerits, it makes a very solid solution. But if you’re only running on commodity hardware, I’d recommend something that will ensure your data’s integrity like any of the others on this list.

Btrfs:

Btrfs is the new kid on the block with a cool jacket and fancy shoes. Btrfs really blows away the competition with a repertoire of features. Btrfs is a filesystem that does not need administration once it has been implemented, that is, you should never have to run an fsck on it. Whenever any errors or inconsistencies arise, it should just handle them on its own and be on its way. That’s a very big value for many, especially those that are not technically able enough to unmount the volume and run a full filesystem check.
In addition to not needing human intervention, it also plays the roles of volume manager and RAID controller. That means that you don’t have to rely on three separate facilities to accomplish robust redundant (or performance) storage anymore, which is a large value to even those that are technically inclined. Btrfs is hailed as the next generation filesystem for Linux users, and it’s easy to see why, though, it does not lend itself to all applications equally without first tweaking the defaults, but it’s surely a good choice for a desktop solution.

ZFS:

ZFS is like the very intimidating nemesis of Btrfs, complete with neck beard. While ZFS predates Btrfs by four or five years, conceptually, they share a lot. ZFS has a very strong track record of reliability and robustness. Although, due to conflicting licenses, it cannot be shipped with Linux, something which Canonical is currently challenging with Ubuntu. As of now, in order to run ZFS, you must install software from third party repositories, and having a ZFS root volume can be very tricky or simply impossible with some distributions. While ZFS is a world-class heavyweight in the domain of filesystems, it is likely that it will always be a foreign resident on Linux systems.
These are just the contemporary filesystems, there are many other filesystems that Linux supports that have either died out or faded away into obscurity like ReiserFS. According to Wiki, there are 36 filesystems supported directly by the Linux kernel including those of Windows and OS X and at least a couple dozen more through FUSE.
So, I think the one thing that really hasn’t changed since the first time I installed Ubuntu on my computer is the amount of choice. The amount of choice is daunting, but I wouldn’t have it any other way.
What filesystems do fossBytes readers use? Did we miss any big ones? Let us know in the comments below.