Most frequently asked interview questions on linux

Here are some of the linux interview questions and answers that would help you to crack some of the most important and difficult interviews as a beginner.

1. What is the basic difference between Linux and Unix?
Linux is an open source operating system while Unix is a proprietary operating system. Linux is therefore, available for free to download but Unix is a paid OS (most of the versions

2. How can you find the active connections through terminal?
Using the netstat command, it is possible to find the active internet connections with the current machine. It is a command line network utility tool.

3. What is the minimum partition requirement in Linux and enlist them.
There should be minimum two partitions that every Linux distribution should have and these are as follows:
Swap Partition
Root Directory

4. What is the SU command used for in Linux?
The SU command in Linux is used to switch from one user account to another user account. You just need to type sudo su and enter the password to switch to another user account in your Linux system.

5. Tell the command to shut down the system.
The command to shutdown the OS is shutdown -h time. In place of time, you can add a number representing the seconds after which you need to shutdown the system.

 6. What is fork()?
fork() is a system call primarily. It is sued to create a new process from an already active process in the system memory. Therefore, the primary process is called the parent process and the newly created process is called the child process.

7. How many run levels modes are available in Linux operating system?
There are a total of seven run level modes available in linux operating system.

8. What do you mean by Open Source System Softwares?
Open Source Softwares are the ones that are freely available for use. They generally come under the GPL License which enables us to view the source code, manipulate it and use it. However, we cannot resell them.

9. How can you list all the running programs in your Linux system?
The TOP Command can be used to enlist all the running processes in your Linux system. You can types TOP in Linux terminal and you’ll get the details of the current processes in your system.

10. What is the difference between BASH and DOS?
BASH is a Unix shell and a command language. DOS is an abbreviated form for Disk Operating System. It is used in Microsoft systems for Command Line Interface. DOS commands are not case sensitive whereas BASH commands are case sensitive.

11. How can you view the current Swap and RAM memory in your Linux system?
There is a command that can be used in the terminal in Linux operating system. The command is FREE. It enables you to view the currently active RAM and Swap memory in the system.

12. Is it legally acceptable to edit the source code of Linux Ubuntu?
Definitely Yes. Linux Ubuntu currently has a large community who regularly edits the source code for modifications and send it to the Linux team. These changes are reviewed by the core team and implemented in the next version. So, it is possible to edit the source code as it comes under GNU GPL License.

13. Which command is used to enlist the files in a particular directory?
To view the existing files in the current directory, you can use the LS command. It is an abbreviated form for LIST.

14. What is Kernel in Linux?
A Kernel in Linux is an essential part of an OS. It is the core of Linux OS. The Kernel provides basic services and interacts with the User Commands. It is fetching your commands and then retrieving the results from the OS and again sending back to the User.

15. Enlist the types of Kernels.
There are various types of Kernels listed as follows:
Monolithic Kernel
Micro Kernel
Hybrid Kernel

16. Which Program is used to securely login in Linux Operating System?
Secure Shell is used to remotely login in Linux OS. It is also known as SSH. SSH is an encrypted or cyrtographic network protocol. SSH is a good replacement of Telnet, which was previously used in Linux OS for Login purpose.

17. Name the Partition that stores the system configuration files in Linux system.
The partition that stores the system configuration files in Linux OS is /etc.

18. Who is the creator of Linux Operating System?
Linus Torvalds has created the Linux Operating System.

19. Enlist the distributions of Linux.
The different types of Linux distributions are listed as follows:
Linux Mint
Ubuntu
Mandriva
Arch
Slackware
Debian
Fedora

20. Where is the user password stored in Linux Operating System?
The User passwords are stored in the directory /etc/passwd

21. In Linux OS, which Daemon controls the Printer Spooling process.
The Line Printing Daemon, also known as LPD controls the Printer Spooling Process.

22. Enlist the filesystems supported in Linux OS.
The filesystems supported by Linux are as follows:
XFS
EXT3
NFS
RAMFS
EXT4
AUTOFS
NTFS

23. What is GNU GPL License?
The GNU General Public License is a Free Software License. This License enables the Users to share, copy, manipulate the code of the software. Therefore, the software code is available for free.

24. Which command is used to delete the files in Linux through command line?
The command used to delete the files in linux is rm.

25. Name the command used to remove the directory.
The command used to remove the directory is rmdir.

26. What should be the size of Swap memory in Linux?
Usually, the size of the Swap memory in Linux Systems should be equal or more two times that of RAM.

27. Explain SE-Linux.
SE – Linux is an abbreviated form for Security Enhanced – Linux. It has been developed to prevent Illegal Daemons and Server Misconfigurations. It provides access control implementation. It implements access authorities to daemons, programs for the files that they can access. The Security Enhanced – Linux provides Security Policy formation.

28. Who is the inventor of Unix Operating System?
The Unix Operating System is created by Dennis Ritchie and Ken Thompson at Bell Labs in 1969.

29. What is the default text editor for Linux?
The default editor for text files in Linux operating system is VI Editor. It can be used to edit any ASCII Text.

30. Name the argument to extract the files from archives using Linux Terminal.
To extract the files from archives, there can be a combination of multiple commands. If you’re trying to extract using TAR Command, then you have to use -x argument with it.

31. What is a Package Manager?
A Package Manager in Linux is a collection of softwares which provides Upgradation, Modification, Removal, Installation and Deletion of programs from the Linux Operating System. It is also known as Package Management System. It is especially developed to automatically install and update the system softwares.

32. What is the name of the Boot Loader in Linux Ubuntu Operating System?
The Boot Loader in Linux Ubuntu OS is called as GRUB Boot Loader.

33. How do you move from one directory to another directory in Linux Operating System?
By using the CD command in Linux Terminal, the user can move from one directory to another one. CD is an abbreviated form of Change Directory.

34. What is Sudo Command?
Sudo command is used to provide highest level access authority to the users. If you use a command in the Linux terminal, you may get an Access Denied output. If you want to make the terminal process a command, you can use the prefix SUDO to get administrator rights for the same.

35. What is Shell?
The Shell is basically an interface between the User Commands and the Operating System. Whatever the user types in is interpreted by the Shell and is then sent to the Operating System Kernel for fetching the results. It converts them to the System Calls.

36. Enlist boot files in Linux Operating System.
The files that are loaded a boot time in Linux OS are as follows:
/etc/fstab
/etc/init.d/rc.d/rcN.d
/boot/grub/grub.conf
/etc/initab

37. How can you find the Run – Level of Linux Operating System?
By using the runlevel command from the Linux Terminal, you can find the Run Level of your Linux  system.

38. Enlist the command to install any software in Linux Ubuntu OS.
The command to install any software in Linux OS is as follows:
sudo apt install application-name

39. How can you terminate a currently executing process in Ubuntu terminal?
The key combination Ctrl + Z allows you to terminate a currently executing process in the Linux Ubuntu Terminal.

40. Which command can be used to monitor Linux ports?
The Nmap localhost command is used to monitor ports in Linux Operating Systems.

41. Enlist the Run Level Modes in Linux.
The Run Level Modes in Linux are as follows:
Halt
Reboot
Single User Mode
Undefined
Multi – User Mode
X11
Multi User Mode with Networking

42. What is the core of Linux OS?
The Linux Kernel is the core of Linux Operating System.