20 Linux Interview Questions with Answers 
1. What is the root account?
Answer: The root account is like a systems administrator account and allows you full control of the system. Here you can create and maintain user accounts, assigning different permissions for each account. It is the default account every time you install Linux.
2. What are the features of the Linux operating system?
Answer: The following are some of the important features of the LINUX operating system:
- Linux Kernel and application programs can be installed on any kind of hardware platform and thus are considered portable.
- It serves the purpose of multitasking by serving various functions simultaneously.
- It provides security services in three ways namely, Authentication, Authorization, and Encryption.
- It supports multiple users to access the same system resource but by using different terminals for operation.
- Linux provides a hierarchical file system and its code is freely available to all.
- It has its own application support (to download and install applications) and customized keyboards.
- Linux distros provide live CD/USB to their users for installation.
3. What is GUI and what are its advantages?
Answer: GUI stands for Graphical User Interface. Its advantages are as follows:
- It allows users to navigate and operate the software with the help of visual elements.
- The more intuitive and rich interface is possible to be created.
- Fewer chances of occurrence of errors as complex, multi-step, dependent tasks are easily grouped together.
- Productivity is enhanced with the means of multitasking as with a simple click of the mouse, the user is able to maintain multiple open applications and transitions between them.
4. What is CLI and what are its advantages?
Answer: CLI stands for Command Line Interface. The advantages are as follows:
- Very flexible
- Can easily access commands
- Much faster and easier to use by expert
- It does not use much CPU processing time.
5. What are the disadvantages of CLI?
- Learning and remembering type commands is hard.
- Have to be typed precisely.
- It can be very confusing.
- Surfing web, graphics, etc are a few tasks that are hard or impossible to do on the command line.
6. What is LILO?
Answer: LILO stands for Linux Loader and is a boot loader to load the operating system in the main memory.
7. What is Linux Kernel?
Answer: Linux Kernel is low-level system software. It is used to manage the hardware resources for the users. It provides an interface for user-level interaction.
8. What is a swap space?
Answer: Swap space is a certain amount of space used by Linux to temporarily hold some programs that are running concurrently. This happens when RAM does not have enough memory to hold all programs that are executing.
9. What are symbolic links?
Answer: Symbolic links act similarly to shortcuts in Windows. Such links point to programs, files or directories. It also allows you instant access to it without having to go directly to the entire pathname.
10. What is the maximum length for a filename under Linux?
Answer: Any filename can have a maximum of 255 characters. This limit does not include the path name, so therefore the entire pathname and filename could well exceed 255 characters.
11. What is redirection?
Answer: Redirection can be defined as changing the standard input and output devices. To redirect metacharacters are used, you can redirect the file or program.
12. What are the File Permission groups in Linux?
Answer: There are three user-based permission groups for each file and directory. They are as follows:
- Owner: Owners only will have to access the file or directory, they will not impact the actions of other users.
- Group: These permissions apply only to the group that has been assigned to the file or directory. They will not impact the actions of other users.
- All Users: These permissions are applied to all users on the system.
13. What are the different modes of Network bonding in Linux?
- Mode-0(balance-rr): It is a default mode and based on Round-Robin policy. It offers fault tolerance and load balancing features. It used round-robin fashion to transmit the packets.
- Mode-1(active-backup): It is based on Active Backup policy and only one slave will act in the band and another one will act when the others fail in the band. It also provides fault tolerance.
- Mode-2(balance-xor): It sets a xor mode between the source Mac address and destination Mac address to provide fault tolerance.
- Mode-3(broadcast): It is based on broadcast policy and transmitted everything in the slave interface. It also provides fault tolerance and can be used only for a particular purpose.
- Mode-4(802.3ad): It is a dynamic aggregation mode, it created aggregation groups which is having the same speed. It uses transmit hashing method to select the slaves for outgoing traffic.
- Mode-5(balance-tlb): The outgoing traffic is according to the current load on the slave, and the incoming traffic is received by the slave. It is called an adaptive transmit load balancing mode.
- Mode-6(balance-alb): It is an adaptive load balancing mode. It does not require any switch support.
14. What are inode and process id?
Answer: The inode is a unique name given to each file and the process id is a unique name given to each process.
15. How is the default run level in Linux changed?
Answer: To change the default run level in Linux use the init command.
16. What is grep command in Linux?
Answer: grep command is a filter that is used to the global search for regular expressions. You can grep command to find errors and exception in log files. I often use grep command with variety of commands like with ps and with netstat to find the things I want. For example ps -ef output every process and if you want just Java process you can filter the output using grep -i "Java"
17. What is the env command in Linux?
Answer: env is a shell command which is used to print a list of current environmental variables.
18. What is the netstat command in Linux?
Answer: netstat command gives various information about the network and routing tables, interface statics and more about the system.
19. What does BASH stand for?
Answer: BASH stands for Bourne Again Shell. It's one of the most popular shell on Linux and you will often find writing bash scripts for automating task in Linux
20. You are working in a client server application and your application is not up, yo suspect its because server is down? how will you check if the server application which runs on remote host is up or not?
Answer: You can use ping command to first check if server is accessible then you can use telnet command to check if your server application is up, running and accepting connections or not.
You can run
$ telnet hostname port
(here hostname and port is remove server host and port)If you just see "trying ........." means host is not reachable and something is wrong with the network may network link issue or any firewall rule issue, you need to involve the network team here for further diagnosis. This is a also a common debugging technique when you support a client server application like FIX Engines which connects to broker to send orders and receives trade.
That's all about Linux Interview Questions for Developers and DevOps in 2022. Finally, I have to tell you that you are now good to go and face the interview panel especially after keenly going through the questions with answers listed above.
They are the right choice of questions that will play a big role towards you passing your interview. Just make sure that you remember the answers when you get to the interview and you will have all the reasons to smile more than ever. Good luck to you.
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