Today i will show you the top 30 important LINUX topics which will be very helpful for your interviews. I have compiled the topics keeping in mind that your are about to appear in an upcoming interview.

Remember, all these 30 topics can be covered in just one day.

Top 30 LINUX topics :

1. Linux and it’s features.
   This includes what LINUX is and what are it’s features like it is fully customizable and Open Source, etc.
   
2. Why to use LINUX?
   If somebody asks you why do you prefer LINUX, then you should convince him/her by talking about the advantages that LINUX have over other OS.
   
3. Familiarization with some common linux technologies (not the Commands, unless mentioned in CV) like what is a terminal, CLI, etc…
   This topic is not very important, so you can complete other topics and comeback again to learn this topic.
   
4. Daemon Processes and VDI(Virtual Desktop Interface).
   Learn about what are daemon processes and VDI.
   
5. Basics of Absolute Path and Local Path and their differences(Basic understanding).
   
6. User Modes in LINUX(like sudo and others).
   
7. Tasks and Threads.
   Read about the concepts of Tasks and Threads, how to kill a task, how to create a thread.
   
8. Major No. and Minor No. in device drivers.
   Just take a look at what this means. You don’t have to dive deep into this topic.
   
9. Context Switching in LINUX.
   The concept is similar to what you might have studied in your Operating Systems classes, so you don’t have to read this topic explicitly.
   
10. Process Descriptors in LINUX.
    
11. Process States – (Running, Stopped, Zombie, Dead, etc…)
    Learn about different states of a process with diagram for clear understanding.
    
12. Time Sharing vs Priority Scheduling Algorithms.
    
13. Linux File Systems structural diagram.
    Here, you should read about the diagramatic representation of memory. Like memory can be represented in terms of Blocks. Blocks together forms Tracks and Sectors and from that Platters and Cylinders and formed. You should memorize this topic well.
    
14. How Linux read and writes are done(Like using head on tracks in rotating type hard disk drives, etc).
    
15. Tree Diagram for File Systems. Just see how the file system is distributed in the tree structure(no need to memorize it).
    
16. File System Blocks.
    Read about Boot Block, Super Block, Data Block, INode Block and understand the functions of each block along with diagram.
    
17. Definition of INode and Inode structure(single indirect, double indirect, triple indirect) with diagram. Also read about how the mapping is done as computer starts, which part will load first and what will be the sequence of reading.
    One more important topic is how files are stored in linux and how files are read from a location and how INode is playing a role in it.
    
18. Users and Groups in Linux.
    Study about significance of /etc/password and /etc/shadow.
    
19. File Permissions in LINUX.
    Since different users have different access rights and permissions(read r, write w, execute x) and file permission representation.Also study how to represent file permissions as numbers.
    
20. chmod, chgrp, chown (just take a look at these commands).
    
21. Umask – defines permissions for a newly created file. If we change the Umask value, then the file permissions for furthur newly created files will change.
    You don’t have to study this topic anywhere else because it’s already explained here.
    
22. SUID, SGID, Sticky Bits (just take a look about what is it and what is does).
    
23. System Calls.
    What calls are system calls, how will you identify a system call. Some examples of system calls are read and write system calls.You should also read about advantages and disadvantages of system calls.
    
24. System Calls and Library functions, difference between them and pros and cons of each.
    
25. File Descriptor Table(FD table).
    Read about what is an FD table and how it is used.
    
26. getrlimit and setrlimit.
    This is not so important topic so you may want to skip this.
    
27. NICE values.
    Carefully read about the NICE values, which indicates the priority of a running process.
    
28. FORK.
    Read about FORK() and some MCQs on FORK().
    
29. PIPE (only basic concepts).
    Read about what is PIPE and how it is used in Linux.
    
30. Basics of IPC.
    Read about the basics of shared memory and message queue.
    

If you have some more spare time left with you, you can also read about Linux Dynamic Priority Algorithm and Realtime Scheduler.
You may also want to search for top 30 or top 50 linux interview questions but i have seen that many of the questions are irrelevant and will never asked in the interviews. So make sure to study topicwise.
You will just be asked some basic questions in your interviews.

So, these were all my personal filtered questions. There are more important qusetions as well but if you don’t get time, then i would highly suggest you to read the above topics.
I hope you will complete all these 30 topics before your interview, so GOOD LUCK to you.