linux Interview Questions and Answers

linux Interview Questions and Answers

1 . What are basic elements or components of Linux?
Linux generally consists of five basic elements or components as given below:

Kernel: It is considered a core or main part of Linux and is generally responsible for all major activities of OS such as process management, device management, etc.
System Library: These are special functions or programs with the help of which application programs or system utilities can access features of the kernel without any requirement of code. It is simply used to implement the functionality of the OS.
System Utility: These are utility programs that are responsible to perform specialized and individual level tasks. They are considered more liable and allow users to manage the computer.
Hardware: It is physical hardware that includes items such as a mouse, keyboard, display, CPU, etc. Shell: It is an environment in which we can run our commands, shell scripts, and programs. It is an interface between user and kernel that hides all complexities of functions of the kernel from the user. It is used to execute commands.

2 What is BASH?

BASH (Bourne Again Shell) is basically a command language interpreter. It was written by Brian Fox for GNU OS and can be used in place of Bourne Shell. It is similar to Bourne Shell but includes some additional features such as command-line editing that make it easier and more convenient to use. It is the default user shell on most Linux installations. It is basically an interpreted and non-compiled process that can also run in the terminal window. It is also capable of reading commands from shell scripts.

3. What is Kernel? Explain its functions.

A kernel is considered the main component of Linux OS. It is simply a resource manager that acts as a bridge between hardware and software. Its main role is to manage hardware resources for users and is generally used to provide an interface for user-level interaction. A kernel is the first program that is loaded whenever a computer system starts. It is also referred to as low-level system software.
• Its other main functions include:
• Memory Management
• Process Management • Device Management
• Storage Management
• Manage access, and use of various peripherals that are connected to the computer.

4. What are two types of Linux User Mode?

There are two types of Linux user mode as given below:
Command Line
GUI

5.What is LILO?

LILO (Linux Loader) is basically a boot loader for Linux that is used to load Linux into memory and start the OS. It is also known as a boot manager that facilitates a dual boot of a computer. It can function as either a master boot program or secondary boot program and performs various functions such as locating kernel, identifying other supporting programs, loading memory, and starting the kernel. If you want to use Linux OS, then you need to install a special boot loader i.e., LILO for it as it allows fast boot of Linux OS.

6. What is swap space?

Swap space, as the name suggests, is basically a space on a hard disk that is used when the amount of physical memory or RAM is full. It is considered a substitute for physical memory. Its main function is to substitute disk space for RAM memory when real RAM does not have enough space to hold all programs that are executing, and more space is required. In simple words, it can be used as an extension of RAM by Linux.

7. What do you mean by a Process States in Linux?

Linux Process is a type of process that can be in a number of different states. The process enters these states from start till end. Process states in Linux are as follows:

New/Ready: In this state, a new process is created and is ready to run.
Running: In this state, the process is being executed.
Blocked/Wait: In this state, the process is waiting for input from the user and if doesn’t have resources to run such as memory, file locks, input, then it can remain in a waiting or blocked state.
Terminated/Completed: In this state, the process has completed the execution or terminated by the OS. Zombie: In this state, the process is terminated but information regarding the process still exists and is available in the process table.

8 . What is Linux Shell ? What types of Shells are there in Linux?

Linux shell is a user interface present between user and kernel. It is used for executing commands and communication with Linux OS. Linux shell is basically a program used by users for executing commands. It accepts human-readable commands as input and converts them into kernel understandable language.
Different types of shells are commonly used on typical Linux system as listed below:

CSH (C Shell)
 KSH (Korn Shell)
 BASH (Bourne Again Shell)
 TCSH
 ZSH
 Bourne Shell

9. Name different types of modes used in VI editor.

VI editor (Visual Editor) is basically a default text editor that usually comes with most of the Linux OS. There are basically three types of modes used in VI editor as given below:
 Command Mode/Regular Mode: It is the default mode for the vi editors. It is generally used to type commands that usually perform particular or specific vi functions. To enter this mode from another mode (Insert mode), one must press [esc]. In simple words, it lets you view the content.
 Insertion Mode/Edit Mode: This mode allows you to do text editing, or type text into a file. To enter this mode from another mode (command mode), one must press [esc]. In simple words, it lets you delete or insert text or content.
 Ex Mode/Replacement Mode: This mode is generally used to save the files and execution of the commands. It basically executes files with different parameters. To enter this mode, one must press [:]. In simple words, it lets you overwrite content or text.

10. What is a maximum length for a filename under Linux?

The maximum length for a filename under Linux is 255 bytes.

11. Name the Linux that is specially designed by Sun micro system.

Linux that is specially designed by Sun micro system is Solaris.

12. Under the Linux system, what is the typical size for swap partitions?

The typical size for a swap partition under a Linux system should be twice the amount of physical memory or RAM available on the system.

13 . What are file permissions in Linux? Name different types of file systems in Linux?

There are three owners in the Linux System i.e., user, group, and others. These owners have three types of permissions defined as listed below:

Read (r): It allows the user to open and read the file or list the directory.
 Write (w): It allows the user to open and modify the file. One can also add new files to the directory.
 Execute (x): It allows the user to execute or run the file. One can also lookup a specific file within a directory.
14. Name the file that is used to automatically mount file systems?
File that is used to automatically mount file systems is a Fstab file.

15. what is LVM and why is it required?

LVM (Logical Volume Management) is basically a tool that provides logical volume management for the Linux kernel. It is being introduced simply to make physical storage device management easier. It also includes allocating disks, striping, mirroring, resizing logical volumes. Its main advantages are increased abstraction, flexibility, and control. It simply allows for flexible disk space management. It is especially required to resize the size of the file system online. In Linux, the size of the LVM partition can be extended using “lvextend” command and can be reduced using “lvreduce” commands, respectively.

16. What is a “/proc” file system?

Proc file system is a pseudo or virtual file system that provides an interface to the kernel data structure. It generally includes useful information about processes that are running currently. It can also be used to change some kernel parameters at runtime or during execution. It is also regarded as a control and information center for the kernel. All files under this directory are named virtual files.

17. What do you mean by the daemons?

Daemons also referred to as the background process, is a long-running Linux program that runs in the background. They do not have any controlling terminal, therefore, they run in the background. These are the processes that are generally started when the system is bootstrapped and terminate or end only when the system is shut down. It is simply the way of extending the functionality of the base OS. It provides and offers several functions that are not available in OS. Its main purpose is to handle periodic requests and then forward the requests to the appropriate programs for execution.

18. Name daemon that controls the print spooling process.

The daemon that controls that print spooling process is the Line printing daemon.

19. Whatis a Zombie Process?

Zombie Process, also referred to as a defunct or dead process in Linux, is a process that has finished the execution, but its entry remains in the process table. It usually happens due to a lack of correspondence between parent and child processes. This process occurs for the child process because the parent process needs to read the status of the child process. Once it is completed using the wait system call, this process is removed from the process table.

20. What is the difference between cron and anacron?

Croon: It is a program in Linux that is used to execute tasks at a scheduled time. It works effectively on machines that run continuously.
Anacreon: It is a program in Linux that is used to execute tasks at certain intervals. It works effectively on machines that are powered off in a day or week.

21. What is load average in Linux?

Load average, as the name suggests, is the average system load on Linux servers being calculated over a given period of time. The load average of Linux servers can be found using “top” and “uptime” commands. It is simply used to keep track of system resources. It is represented by a decimal number starting at 0.00. It tells you the load that the system has been under.

22 . What do you mean by Shell Script?

Shell Script, as name suggests, is a script especially written for shell. Here, script means programming language that is being used to control applications. It simply allows the execution of different commands that are entered in the shell. It generally helps you to create complex programs containing conditional statements, loops, and functions. It is very easy to debug, can simplify everyday automation processes, and is much quicker as compared to writing big programs.

23. What is INODE and Process Id?

INODE: It is a unique name given to each file by OS. Each inode has a unique inode number within a file system. It stores various information about files in Linux such as ownership, file size, file type, access mode, number of links, etc.
Process Id (Identifier): It is a unique Id given to each process. It is simply used to uniquely identify an active process throughout the system until the process terminates

24. Name the first process that is started by the kernel in Linux and what is its process id?
The first process started by the kernel in Linux is “init” and its process id is 1.

25. What is CLI and GUI?

CLI (Command Line Interface): It is basically a command-line program that usually accepts text as input to execute or run functions of the operating system. It allows users to type declarative commands simply to give instructions to the computer to perform or execute operations. It usually requires less memory to use as compared to other interfaces as well as it does not require Windows and a low-resolution monitor can be used. It usually provides greater flexibility of use and can also be used to perform things easily that are most difficult to do with GUI.
GUI (Graphical User Interface): It is basically a human-computer interface that allows users to interact with electronic devices through graphical icons and visual indicators. The use of these graphical elements or icons makes it easier for users to interact with the system. It is visually intuitive and allows higher productivity. It is usually a combination of graphical and textual interaction that uses menus, buttons, message boxes, etc.

26. Why /etc/resolv.conf and /etc/hosts files are used?

/etc/resolv.conf: It is used to configure DNS name servers as it contains the details of the nameserver i.e., details of your DNS server. The DNS server is then used to resolve the hostname of the IP address.
/etc/hosts: It is used to map or translate any hostname or domain name to its relevant IP address.

27. What are the advantages of using NIC teaming?

 NIC (Network Interface Card) teaming has several advantages as given below: Load Balancing
 Failover
 Increases uptime

28. What do you mean by Network bonding?

Network Bonding, also known as NIC Teaming, is a type of bonding that is used to connect multiple network interfaces into a single interface. It usually improves performance and redundancy simply by increasing network throughput and bandwidth.

29 . What are different network bonding modes used in Linux?

 Different network bonding modes used in Linux are listed below:
 Mode-0 (balance-rr): It is the default mode and is based on round-robin policy. It offers features like fault tolerance and load balancing.
 Mode-1 (active-backup): It is based on an active-backup policy. In this, only one node responds or works at the time of failure of other nodes.
 Mode-2 (balance-xor): It sets an XOR (exclusive-or) mode for providing load balancing and fault tolerance.
 Mode-3 (broadcast): It is based on broadcast policy. It sets a broadcast mode for providing fault tolerance and can be used only for specific purposes.
 Mode-4 (802.3ad): It is based on IEEE 802.3ad standard also known as Dynamic Link Aggregation mode. It sets an IEEE 802.3ad dynamic link aggregation mode and creates aggregation groups that share the same speed and duplex settings.
 Mode-5 (balance-tlb): It is also known as Adaptive TLB (Transmit Load Balancing). It sets TLB mode for fault tolerance and load balancing. In this mode, traffic will be loaded based on each slave of the network.
 Mode-6 (balance-alb): It is also known as Adaptive Load Balancing. It sets ALB mode for fault tolerance and load balancing. It doesn’t need any special switch support.

30. Name default ports used for DNS, SMTP, FTP, SSH, DHCP and squid.

Default ports used for various services are as follows:
Service , Port, DNS
 53
 SMTP
 25
 FTP
 20 (Data transfer), 21 (Connection established )
 SSH
 22
 DHCP
 67/UDP (dhcp server), 68/UDP (dhcp client)
 squid
 3128
31. What is SSH? How we can connect to a remote server via SSH?
SSH (Secure Shell), as the name suggests, is basically a protocol that is being used to securely connect to remote servers or systems and enables two systems to communicate. It is considered the most common way to have access to remote Linux servers. It generally transmits data over encrypted channels therefore security is considered at a high level. To connect to a remote server via SSH, you need to own a domain name and IP address.

32. Write the difference between Soft and Hard links?

Hard Links: It is a special kind of file that points to the same underlying inode as another file. It can be referred to as an additional name for an existing file on Linux OS. Total number of hard links for a file can be displayed using the “ls -l” command. Such links cannot be used across file systems. Hard links can be created using the following command:
$ ln [ original filename] [link name ]
Soft Links: It is also termed a symbolic Link. Soft links are kinds of files that usually point to another file. It does not include any amount of data in the target file and simply points to another entry anywhere in the file system. Such links can be used across file systems. Soft links can be created using the following command:

33. Name three standard streams in Linux?

Standard streams are basically I/O (Input and Output) communication channels between a program and its environment in Linux. Input and output in the Linux environment are distributed across three standard streams. Three standard streams in Linux are as follows:
 Standard Input (stdin)
 Standard Output (stdout)
 Standard Error (stderr)

34. What is netstat command?

netstat (Network statics) command is generally a networking tool being used for troubleshooting and configuration and used to display all network connections on a system. It simply provides a way to check whether various aspects of TCP/IP are working and what connections are present.

35. What is the ping command?

Linux ping (Packet Internet Groper) command is a command that is used to check connection status between source and destination. In simple words, this command is used to check whether a network is available and if the host is reachable. It can also be used to troubleshoot different connectivity issues, verify connectivity at an IP -level to a second TCP/IP device, and name resolution. One can use this command to test both the computer name and IP address of the computer.

36. Which command is used to check the default run level?

The command used to check the default run level is “/etc/inittab”.

37 . Which command is used to check the size of file or directory?

The command used to check the size of the file or directory is “du”. Here “du” stands for disk usage that is used to check information of disk usage of files and directories on a machine. It is also used to display files and directory sizes in a recursive manner.
Example:
$ du -sh /var/log/*
1.8M /var/log/anaconda
384K /var/log/audit
4.0K /var/log/boot.log
0 /var/log/chrony
4.0K /var/log/cron
4.0K /var/log/maillog
64K /var/log/messages

38. Which command is used to count the number of characters in a file?

The command that is used to count the number of characters in a file in Linux is “wc”. Here
“wc” stands for word count. It is used to count the number of lines, words, and characters in a text file.

39. What is the function of grep command?

Grep (Global regular expression print) is a command that is used to the global search for a string of characters in a specified file. The text search pattern is generally known as a regular expression. It simply makes use of pattern-based searching.
Syntax: grep [ options] pattern [files ]
Example: $ grep -c “linux” interview.txt
The above command will usually print the total count of the word “Linux” in the file “interview.txt”.

40. Explain working of env command.

“env” command is basically a shell command that is used to print a list of current environmental variables. Here, “env” stands for the environment. It can also run another process in another environment without any modification of the current environment. It allows you to run programs in a modified environment. It is generally used by shell scripts to launch the correct interpreter. It can also be useful for checking if wrong environment variables prevent the application from starting during troubleshooting.

41. What is the pwd command?

“pwd” command is basically a command that is used to print the complete path of the current working directory starting from the root (/). Here, “pwd” stands for Print Working Directory. It is considered one of the most basic and most used commands in Linux. This command is usually a built-in shell command and is also available in different shells such as bash, ksh, zsh, bourne shell, etc.

42. Name the command that is used to check all the listening ports and services of your machine.

# netstat -ntlp

43. Which command is used to check the memory status?

The command used mostly to check memory status in Linux is “free”. Other commands that can be used are given below:

“cat” command: It can be used to show or display Linux memory information. (cat/proc/meminfo)
 “vistas” command: It can be used to report statistics of virtual memory.
 “top” command: It can be used to check the usage of memory.
 “hop” command: It can be used to find the memory load of each process.
44. What is pipe?

In Linux, a pipe is basically a form of redirection that is used to send the output of one command to another command for further processing. It simply takes the output from one command and uses it as an input for another. It provides asynchronous execution of commands with help of buffered I/O routines.

45. What are Linux directory commands?

There are basically five Linux directory commands that are used to work with files and directories as given below:
 pwd: It stands for “print working directory”. This command is generally used to display the path of the present or current working directory. Syntax: $ pwd
 cd: It stands for “change directory”. This command is generally used to change the present working directory to the directory that we want to work on. Syntax: $ cd <path to new directory>
 Is: It stands for “list”. This command is generally used to show the full list of content of files and directories in the present working directory. Syntax: $ ls
 mkdir: It stands for “make directory”. This command generally allows users to create directories in Linux.
Syntax: $ mkdir <name (and path if required) of new directory>
 rmdir: It stands for “remove directory”. This command is used to remove/delete each directory that is specified on the command line.
Syntax: $ rmdir <name (and path if required) of directory>

46 . What do you mean by unmask?

Unmask, also known as user file-creation mask, is a Linux command that allows you to set up default permissions for new files and folders that you create. In Linux OS, unmask command is used to set default file and folder permission. It is also used by other commands in Linux like mkdir, tee, touch, etc. that create files and directories.
Syntax: unmask [-p] [-S] [mask]
Where,
[ mask]: It represents the permission masks that you are applying.
[-S]: It displays the current mask as a symbolic value.
[-p]: It displays the current mask along with unmask command thus allowing it to be copied and pasted as a future input.

47. Name the command used to review boot messages?

The command that is used to review boot messages is the “dmesg” command.

48 . Write difference between Linux and Unix?

 Linux: It is an open-source and free-to-use Operating system that was first developed in 1991 by Linus Torvalds. It is specially designed to offer free and low-cost OS for personal computer users. It has very low hardware requirements and facilitates powerful support for networking. Different versions of Linux are known as variants. Example: Red Hat, Android, etc.
 Unix: It is a closed source OS derived from the original AT&T Unix and was first developed in the 1960s. It is not open source and is not free to use. It is generally capable of handling activities from multiple users at the same time. Furthermore, it is specially designed to be more portable, multi-user, and multitasking in a time-sharing configuration. Different versions of Unix are known as distros.
Example: HP-UX, Solaris, etc.

49 . What is the difference between BASH and DOS?

BASH (Bourne Again Shell): It is basically a powerful command shell and scripting language that is being developed from the Bourne shell used on UNIX systems. It runs on multiple OS and new features are added regularly. It can read and execute commands from a file known as a shell script.
DOS (Disk Operating System): It is basically an OS that runs from a hard disk drive. It was the first OS system used by IBM-compatible computers. It basically provides a command-line in which users are allowed to give instructions in the form of commands.
50. What is samba? Why is it required?

Samba is basically an open-source software suite. It runs a number of different Operating systems such as OpenVMS, IBM , etc. It is generally used to connect Linux machines to Microsoft network resources simply by providing Microsoft SMB support. It provides more secure, stable, fast file and print services for every client or user using SMB (Server Message Block) or CIFS (Central Server Message Block) protocol.

51. Conclusion?

Linux, like windows, iOS, and Mac, is an operating system that helps one to use or utilize old and outdated computer systems such as Firewall, router, backup server, etc. It makes computer systems more secure than Windows and does not require any use of Anti-Virus Programs. It is becoming increasingly popular as the OS for servers because it comes with the capabilities to heavily encrypt and protect all of a computer’s data. The above given are all important questions along with answers related to Linux that were recently asked in Interviews. It will give you a better understanding of all the important topics related to Linux and will help you to crack the interviews.

52.Is it legal to edit the Linux kernel?

Yes, as it is under General Public License (GPL), and anyone can edit.

53.What is LILO?

LILO stands for Linux Loader and is a boot loader to load the operating system in the main memory.

54.What are the basic components of Linux?

This is one of the popularly asked interview questions on Linux. The Linux operating systemconsists of the following three components:
1. Kernel: It is the core part of Linux and is responsible for all major activities of the operating system. Linux Kernel is free and open-source software that manages hardware resources for the users. It consists of various modules and interacts directly with the underlying hardware. Kernels prevent conflicts between different processes. Different types of the kernel are:
 Monolithic kernels
 Exo kernels
 Hybrid kernels
 Micro kernels
2. System Library: System libraries are special functions using which application programs access Kernel’s features. System libraries are responsible for implementing most of the functionalities of the operating system. They do not require kernel module’s code access rights.
3. System Utility: These programs are responsible for performing specialized, individual-level tasks.

55.What is BASH?

BASH is short for Bourne Again SHell. Written by Steve Bourne, it acts as the default shell for most Linux systems since it has been adapted.

56. What is the difference between BASH and DOS?

This is one of the most commonly asked Linux interview questions.
There are three key differences between BASH and DOS:
BASH commands are case sensitive while DOS commands are not
BASH follows no convention in naming files, while DOS follows a convention
Under BASH, / character serves as a directory separator while in DOS \ serves as the directory separator.

57 .What is the root account in Linux?

The root account is like a systems administrator account and allows full control of the system.

58 .How can you find out how much memory Linux is using?

From a command shell, use the “concatenate” command: cat /proc/meminfo for memory usage information.

59.What is the difference between internal and external commands?

Internal commands are those that are already loaded in the system. External commands are those which can be executed at any time and are independent.

60.Which daemon controls the print spooling process?

The line printing daemon lpd is the line printer daemon (spool area handler) and is normally invoked at boot time from the rc(8) file.

61.What is the procedure to set the umask permanently for a user?

If the umask command is used without any arguments, it means it will display the current mask.
There are two types to set the umask permanently:
1. Ocotal representation.
2. Symbolic representation.

62 .What is the procedure to convert the default run level in Linux?

To convert the default run level in Linux, we can use the init command.

63.How to share a directory with the help of nfs?

To share a directory with the help of NFS, we have to edit the configuration file,
‘/etc/exports’, and add an entry like directory name ‘/’. Then, restart the NFS service.

64. How can we lock the user account in Linux?

We can lock user account for the security of users so that unauthorized users cannot log in. There are a few ways to lock the user account:
 Disable the password with the help of passwd command.
 Delete the user account with the help of usermod command or change command.
 Switching the shell using nologin command ( /sbin/nologin ).

65. Explain the grep command in Linux?

grep command is used to the global search for regular expressions.

66.What is the role of the cp command in Linux?

cp command in Linux is used to copy files and directories. We can also use it for the backup of files or directories.

67 .How to delete a directory in Linux?

 The rmdir and rm commands are used to remove a directory in Linux.
 rmdir command deletes the empty directory.
Syntax:
 rmdir [-p] [-v | –verbose] [–ignore-fail-on-non-empty] directories rm command deletes non-empty directories and their contents.
Syntax:
 rm -rf dir-name rm -rf /path/to/dir/name

68. Mention some Linux file content commands?

Following are some file content commands:
 head: Display the top lines of the file.
 tail: Display the last lines of the file.
 cat: Concatenate more than two files.
 more: Display the content in pager form to view in the terminal.

69.Explain what PIPE in Linux is?

 A pipe is a form of redirection in Linux, it is mainly used to combine two or more than two commands, and the output of one command can take as input to the next command.
 Syntax:
 command_1 | command_2 | command_3 | …. | command_N

70.Explain lsof command in Linux?

lsof command is used to list the open files assigned to the application. It also lists the processes that opened them.

71.Explain the df command in Linux?

The df (display free disk space) command is used to troubleshoot disk space problems.

72. Explain what does (cd dir && command) do?

The cd dir && command moved to the dir and used to execute the command, then returns to the current directory.

73.What is the role of pushd command in Linux?

The pushd command is used to put recent dir on the stack so that it can pop back to it.

74 .What is the role of pwd command?

The pwd or print working directory command is one of the commonly used commands in Linux. It is used to write the full pathname of the current working directory. It will print the path of the working directory starting from the root.

75.What is CLI? What are its advantages and disadvantages?

This is one of the most important Linux interview questions for experienced candidates. CLI stands for Command Line Interface. It is a non-graphical, text-based interface that enables users to interact with computers. Using the Linux interface, users can type declarative commands and instruct the computer to perform operations. It is based on the response transaction process and offers great flexibility.
Advantages of CLI :
 A lot faster and efficient to use by experts (those who know the commands).
 Offers great flexibility.
 Does not use much CPU processing time.
 Does not require Windows to run.
 Needs fewer resources.
 Needs much less memory (Random Access Memory).
Disadvantages of CLI:
It can be very confusing for new users.
 Requires a lot of commands to be learned and remembered.
 Commands need to be typed precisely. If there is a spelling mistake then the command will not respond or fail.

76. What are symbolic links?

A symbolic link or symlink in Linux is a file that points to another file or a folder on the computer. It functions like shortcuts in Windows. It enables you to instantly access programs, files, or directories without having to go directly to the entire pathname. Symbolic links are also called ‘soft links’.
Features of Symbolic Links:
A symbolic link is similar to the file shortcut feature in Windows Operating systems.
They can be linked across different file systems.
They contain the path for the original file and not the contents.
Syntax:
ln -s [target file] [Symbolic filename]
-s – to create a soft (symbolic) link
[target file] – the name of the existing file for which you are creating the link
[Symbolic filename] – the name of the symbolic link
77.How do you change permissions under Linux?
chmod (change mode) command is used to change file and directory permissions in Linux.
The chmod command consists of at least three parts from the following:
Example:
 chmod +rwx filename to add permissions.
 chmod -rwx directoryname to remove permissions.
 chmod +x filename to allow executable permissions.
 chmod -wx filename to take out write and executable permissions.

78. What are the features of Linux?

This is one of the basic Linux interview questions that you must prepare for your interview.
Following are some of the features of Linux:
1. Multitasking: Supports more than one function simultaneously by dividing the CPU time.
2. Multiuser capability: Allows multiple users to access the same system resource using different terminals for operation.
3. Portable: Linux Kernel and application programs can be installed on any kind of hardware platform.
4. Application support: Has its own software repository to download and install applications.
5. Security: Provides security in three ways namely, authentication, authorization, and encryption.
6. Hierarchical File System: Provides a standard file structure in which system files and user files are arranged.
7. Open Source: Code is freely available to all.
8. Live CD/USB: Provide a live CD/USB so that users can run it without installing it.

79.What are the different types of Process Management System Calls in Linux?

Process management uses certain system calls. They are:
 fork ()
 create a new process
 exec ()
 execute a new process
 wait()
 wait until process execution
 exit()
 terminate the process
 getpid ()
 to find the unique process id
 getppid()
 to find the parent process id
 nice ()
 bias the currently running process property

80. What is Kali Linux?

Formerly known as BackTrack Linux, Kali Linux is an open-source, Debian-based Linux distribution for penetration testing and security auditing. It was launched in March 2013. It is a rebuild of BackTrack Linux that conforms to Debian development standards. Kali Linux offers a wide variety of tools for information security tasks such as Penetration Testing, Computer Forensics, and Security Research.
Below are some key features of Kali Linux:
 Accessible
 Multi-platform solution
 Completely free of charge
 Custom Linux Kernel
 Comes with a vast array of penetration testing tools
 FHS compliant
 Multi-language support
 Customizable
 Can be used on a variety of ARM Devices

81. Why is Linux better than Windows?

Linux offers more security and great speed compared to Windows. Windows offers great ease of use, enabling even non-technical people to work on it easily. But it is less secure compared to Linux as viruses and malware affect windows more quickly. Linux is preferred by many corporate organizations as a server and operating system for security.

82. Which Shells are used in Linux?

Some of the commonly used Shells in Linux are:
A. Bash: It stands for Bourne Again Shell. It is the default for most Linux distributions.
B. Ksh: Ksh stands for Korn shell. It is a high-level programming language shell.
C. Csh: The C Shell follows C-like syntax. It offers spelling correction and job control. D. Zsh: Z Shell is an interactive shell that offers some unique features like startup files, login/logout watching, closing comments, and more. It incorporates some features of other Linux shells such as Bash and Ksh.
E. Fish: It stands for Friendly Interactive Shell and provides some unique features like man page completions, web-based configuration, auto-suggestions, and fully scriptable with clean scripts. It is fully interactive and user-friendly like other shells.

83.What are the different process states in Linux?

This is a popular Linux interview question that must prepare for Ready: The process has been created and is ready to run.
 Running: The process is being executed and using the CPU at a particular moment.
 Waiting: Process is waiting for an event to occur or for a system resource.
 Terminated/Stopped: A process has been stopped, usually by receiving a signal.
 Zombie: The process is terminated, but still has an entry in the process table.
84. What are Daemons in Linux?

This is another popular Linux interview question. Daemons are the programs on Unixlike operating systems that run in the background instead of running under the direct control of a user. In Linux, daemons extend the functionality of the base operating system by offering functions that might not be available in the operating system.
A daemon actively listens for a service request and acts upon it at the same time. On completion of service, the daemon gets disconnected and waits for further requests.
Most have a ‘d’ at the end of the process name. Some of the service daemons for Linux systems are:
amd – Auto Mount Daemon ftpd – FTP Server Daemon httpd – Web Server Daemon mysql – Database server Daemon nfsd – Network File Sharing Daemon sshd – Secure Shell Server Daemon

85.What is Graphical User Interface?

Graphical User Interface is a human-computer interface that allows interaction between users and electronic devices through visual indicators and graphical icons. Users can easily interact with the system through these graphical elements or icons. It is visually intuitive and leads to higher productivity. It is a combination of textual and graphical interaction that uses buttons, menus, message boxes, etc.

Redirection refers to the process of directing data from one output to another.

87.What is Secure Shell (SSH)? How can we connect to a remote server through Secure Shell?

Secure Shell (SSH) is a protocol used for securely connecting to remote servers and to enable communication between two systems. It is one of the most common methods to have access to remote Linux servers. It transmits data over encrypted channels leading to high-level security. To connect to a remote server through a secure shell (SSH), you will require a domain name and IP address.

88.Write the difference between Soft and Hard links?

Soft Links or Symbolic Link are different types of files that point towards another file. It does not include any data in the target file and points towards another entry anywhere within the file system. These links can be used across the file systems. Soft links can be created through the following command:
Hard Links are special type of files that point towards same underlying inode as another file. It can be referred to as an additional name for the existing file on Linux OS. The total number of hard links for a file are displayed through the “ls -l” command. These links cannot be used across file systems and can be created through the following command:

89. What is the difference between UNIX and LINUX?

Unix originally began as a propriety operating system from Bell Laboratories, which later on spawned into different commercial versions. On the other hand, Linux is free, open source and intended as a non-propriety operating system for the masses.

90. What is BASH?

BASH is short for Bourne Again SHell. It was written by Steve Bourne as a replacement to the original Bourne Shell (represented by /bin/sh). It combines all the features from the original version of Bourne Shell, plus additional functions to make it easier and more convenient to use. It has since been adapted as the default shell for most systems running Linux.

91. What is Linux Kernel?

The Linux Kernel is a low-level systems software whose main role is to manage hardware resources for the user. It is also used to provide an interface for user-level interaction.

92. What is LILO?

LILO is a boot loader for Linux. It is used mainly to load the Linux operating system into main memory so that it can begin its operations.

93. What is a swap space?

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.

94. What is the advantage of open source?

Open source allows you to distribute your software, including source codes freely to anyone who is interested. People would then be able to add features and even debug and correct errors that are in the source code. They can even make it run better and then redistribute these enhanced source code freely again. This eventually benefits everyone in the community.

95 .What are the basic components of Linux?

Just like any other typical operating system, Linux has all of these components: kernel, shells and GUIs, system utilities, and an application program. What makes Linux advantageous over other operating system is that every aspect comes with additional features and all codes for these are downloadable for free.

96.Does it help for a Linux system to have multiple desktop environments installed?

In general, one desktop environment, like KDE or Gnome, is good enough to operate without issues. It’s all a matter of preference for the user, although the system allows switching from one environment to another. Some programs will work in one environment and not work on the other, so it could also be considered a factor in selecting which environment to use.

97 .What is the basic difference between BASH and DOS?

 The key differences between the BASH and DOS console lie in 3 areas:
 – BASH commands are case sensitive while DOS commands are not;
 – Under BASH, / character is a directory separator and \ acts as an escape character.
Under DOS, / serves as a command argument delimiter and \ is the directory separator
 – DOS follows a convention in naming files, which is 8 character file name followed by a dot and 3 characters for the extension. BASH follows no such convention.

98. Describe the root account.

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.

99. What is GUI?

GUI, or Graphical User Interface, make use of images and icons that users click and manipulate as a way of communicating with the computer. Instead of having to remember and type commands, the use of graphical elements makes it easier to interact with the system, as well as adding more attraction through images, icons, and colors.

100. What is CLI?

CLI is short for Command Line Interface. This interface allows the user to type declarative commands to instruct the computer to perform operations. CLI offers greater flexibility. However, other users who are already accustomed to using GUI find it difficult to remember commands including attributes that come with it.

101. How do you open a command prompt when issuing a command?

To open the default shell (which is where the command prompt can be found), press Ctrl-Alt-F1.
This will provide a command line interface (CLI) from which you can run commands as needed.

102 .How can you find out how much memory Linux is using?

From a command shell, use the “concatenate” command: cat /proc/meminfo for memory usage information. You should see a line starting something like Mem: 64655360, etc. This is the total memory Linux thinks it has available to use.
You can also use commands
Free _ m Vmstart top htop
To find current memory usage

103 .What is a typical size for a swap partition under a Linux system?

The preferred size for a swap partition is twice the amount of physical memory available on the system. If this is not possible, then the minimum size should be the same as the amount of memory installed.

104. What are symbolic links?

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.

105. Does the Ctrl+Alt+Del key combination work on Linux?

Yes, it does. Just like Windows, you can use this key combination to perform a system restart. One difference is that you won’t be getting any confirmation message and therefore, a reboot is immediate.

106.How do you refer to the parallel port where devices such as printers are connected?

Whereas under Windows you refer to the parallel port as the LPT port, under Linux you refer to it as /dev/lp . LPT1, LPT2 and LPT3 would therefore be referred to as /dev/lp0, /dev/lp1, or /dev/lp2 under Linux.

107.Are drives such as hard drive and floppy drives represented with drive letters?

No. In Linux, each drive and device have different designations. For example, floppy drives are referred to as /dev/fd0 and /dev/fd1. IDE/EIDE hard drives are referred to as /dev/hda, /dev/hdb, /dev/hdc, and so forth.

108 How do you change permissions under Linux?

Assuming you are the system administrator or the owner of a file or directory, you can grant permission using the chmod command. Use + symbol to add permission or
– symbol to deny permission, along with any of the following letters: u (user), g (group), o (others), a (all), r (read), w (write) and x (execute). For example, the command chmod go+rw FILE1.TXT grants read and write access to the file FILE1.TXT, which is assigned to groups and others.

109 .In Linux, what names are assigned to the different serial ports?

Serial ports are identified as /dev/ttyS0 to /dev/ttyS7. These are the equivalent names of COM1 to COM8 in Windows.

110. How do you access partitions under Linux?

Linux assigns numbers at the end of the drive identifier. For example, if the first IDE hard drive had three primary partitions, they would be named/numbered, /dev/hda1, /dev/hda2 and /dev/hda3.

111. What are hard links?

Hard links point directly to the physical file on disk, and not on the pathname. This means that if you rename or move the original file, the link will not break since the link is for the file itself, not the path where the file is located.

112 .What is the maximum length for a filename under Linux?

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.

113 .What are filenames that are preceded by a dot?

In general, filenames that are preceded by a dot are hidden files. These files can be configuration files that hold important data or setup info. Setting these files as hidden makes it less likely to be accidentally deleted.

114. Explain virtual desktop?

This serves as an alternative to minimizing and maximizing different windows on the current desktop. Using virtual desktops can clear the desktop when you can open one or more programs. Rather than minimizing/restoring all those programs as needed, you can simply shuffle between virtual desktops with programs intact in each one.

115. How do you share a program across different virtual desktops under Linux?

To share a program across different virtual desktops, in the upper left-hand corner of a program window look for an icon that looks like a pushpin. Pressing this button will “pin” that application in place, making it appear in all virtual desktops, in the same position onscreen.

116.What does a nameless (empty) directory represent?

This empty directory name serves as the nameless base of the Linux file system. This serves as an attachment for all other directories, files, drives, and devices.

117. What is the pwd command?

The pwd command is short for print working directory command.

118.What are daemons?

Daemons are services that provide several functions that may not be available under the base operating system. Its main task is to listen for service request and at the same time to act on these requests. After the service is done, it is then disconnected and waits for further requests.

119.How do you switch from one desktop environment to another, such as switching from KDE to Gnome?

Assuming you have these two environments installed, just log out from the graphical interface. Then at the login screen, type your login ID and password and choose which session type you wish to load. This choice will remain your default until you change it to something else.

120. What are the kinds of permissions under Linux?

There are 3 kinds of permissions under Linux:- Read: users may read the files or list the directory- Write: users may write to the file of new files to the directory- Execute: users may run the file or lookup a specific file within a directory

121 .How does case sensitivity affect the way you use commands?

When we talk about case sensitivity, commands are considered identical only if every character is encoded as is, including lowercase and uppercase letters. This means that CD, cd, and Cd are three different commands. Entering a command using uppercase letters, where it should be in lowercase, will produce different outputs.

122.What are environmental variables?

Environmental variables are global settings that control the shell’s function as well as that of other Linux programs. Another common term for environmental variables is global shell variables.

123.What are the different modes when using vi editor?

There are 3 modes under vi:- Command mode – this is the mode where you start inEdit mode – this is the mode that allows you to do text editing- Ex mode – this is the mode wherein you interact with vi with instructions to process a file

124 .s it possible to use shortcuts for a long pathname?

Yes, there is. A feature known as filename expansion allows you do this using the TAB key. For example, if you have a path named /home/iceman/assignments directory, you would type as follows: /ho[tab]/ice[tab]/assi[tab] . This, however, assumes that the path is unique and that the shell you’re using supports this feature.

125. What is the advantage of open source?

Open source facilitates you to distribute your software, including source codes freely to anyone who is interested. So, you can add features and even debug and correct errors of the source code.

126. What is grip command?

grep a search command that makes use of pattern-based searching. It makes use of options and parameters that are specified along with the command line and applies this pattern in searching the required file output.

127.What could be the problem when a command that was issued gave a different result from the last time it was used?

One highly possible reason for getting different results from what seems to be the same command has something to do with case sensitivity issues. Since Linux is case sensitive, a command that was previously used might have been entered in a different format from the present one. For example, to lists all files in the directory, you should type the command ls, and not LS. Typing LS will either result in an error message if there is no program by that exact name exist or may produce a different output if there is a program named LS that performs another function.

128.What are the contents of /usr/local?

It contains locally installed files. This directory matters in environments where files are stored on the network. Specifically, locally-installed files go to /usr/local/bin, /usr/local/lib, etc.). Another application of this directory is that it is used for software packages installed from source, or software not officially shipped with the distribution.

129. How do you terminate an ongoing process?

Every process in the system is identified by a unique process id or pid. Use the kill command followed by the pid to terminate that process. To terminate all process at once, use kill 0.

130.How do you insert comments in the command line prompt?

Comments are created by typing the # symbol before the actual comment text. This tells the shell to completely ignore what follows. For example “# This is just a comment that the shell will ignore.”

131.What is command grouping and how does it work?

You can use parentheses to group commands. For example, if you want to send the current date and time along with the contents of a file named OUTPUT to a second file named
MYDATES, you can apply command grouping as follows: (date cat OUTPUT) > MYDATES

132.How do you execute more than one command or program from a single command line entry?

You can combine several commands by separating each command or program using a semicolon symbol. For example, you can issue such a series of commands in a single entry:
ls –l cd .. ls –a MYWORK which is equivalent to 3 commands: ls -l cd.. ls -a MYWORK

133. Write a command that will look for files with an extension “c”, and has the occurrence of the string “apple” in it.

Find ./ -name “*.c” | xargs grep –i “apple”

134. What is the command to calculate the size of a folder?

To calculate the size of a folder uses the command du –sh folder1.

135.How can you check the memory status?

You can use the command free -m to display output in MB free -g to display output in GB

136.How can you append one file to another in Linux?

To append one file to another in Linux you can use command cat file2 >> file 1. The operator >> appends the output of the named file or creates the file if it is not created. While another command cat file 1 file 2 > file 3 appends two or more files to one.

137.Explain how you can find a file using Terminal?

To find a file you have to use a command, find . –name “process.txt” . It will look for the current directory for a file called process.txt.

138. Explain how you can create a folder using Terminal?

To create a folder, you have to use command mkdir. It will be something like these: ~$ mkdir Guru99

139 .Explain how you can view the text file using Terminal?

To view the text file, go to the specific folder where the text files are located by using the command cd and then type less filename.txt.

140.Explain how to enable curl on Ubuntu LAMP stack?

To enable curl on Ubuntu, first, install libcurl, once done use following command sudo/etc/init .d /apache2 restart or sudo service apache2 restart.

141.Explain how to enable root logging in Ubuntu?

The command which enables root logging is
#sudo sh-c ‘echo “greater-show-manual-login=true” >>/etc/lightdm/lightdm.conf’

142. How can you run a Linux program in the background simultaneously when you start your Linux Server?

By using nohup. It will stop the process receiving the NOHUP signal and thus terminating it you log out of the program which was invoked with. & runs the process in the background.

143. Explain how to uninstall the libraries in Linux?

To uninstall the libraries in Linux, you can use command sudo apt-get remove library_name

144.What is Linux Kernel? Is it legal to edit Linux Kernel?

Linux kernel refers to the low-level system software. It is used to manage resources and provide an interface for user interaction.
Yes, it is legal to edit Linux Kernel. Linux is released under the General Public License (General Public License). Any project released under GPL can be modified and edited by the end users.

145.What are the basic components of Linux?

Kernel: It is the core component of the Operating System that manages operations and hardware.
Shell: Shell is a Linux interpreter which is used to execute commands.
GUI: GUI stands for Graphical User Interface which is another way for a user to interact with the system. But unlike CLI, GUI consists of Images, Buttons, TextBoxes for interaction. System Utilities: These are the software functions that allows the user to manage the computer.
Application Programs: Software programs or set of functions designed to accomplish a specific task.

146.Explain file permission in Linux.

Read: Allows a user to open and read the file Write: Allows a user to open and modify the file Execute: Allows a user to run the file.

147.  What is Swap Space?

Swap Space is the additional spaced used by Linux that temporarily holds concurrently running programs when the RAM does not have enough space to hold the programs. When you run a program, it resides on the RAM so that the processor can fetch data quickly. Suppose you are running more programs than the RAM can hold, then these running programs are stored in the Swap Space. The processor will now look for data in the RAM and the Swap Space.

148.What is the difference between BASH and DOS?

 BASH
 Commands are case-sensitive.
 Commands are not case-sensitive.
 ‘/’ ( forward slash) is used as a directory separator.
 ” ( backslash) is used as an escape character.
 ‘/’ ( forward slash) is used as command argument delimiter.
 ” ( backslash) is used as a directory separator.
 Follows naming convention: 8 characters for file name postfixed with 3 characters for the extension.
 No naming convention.

149. What command would you use to check how much memory is being used by Linux?

You can use any of the following commands:
I. free – m II. Vmstart
III. Stop
IV. hstop

150.Explain file permission in Linux.

There are 3 kinds of permission in Linux:
1.Read: Allows a user to open and read the file 2.Write: Allows a user to open and modify the file
3.Execute: Allows a user to run the file.
You can change the permission of a file or a directory using the chmodcommand. There are two modes of using the chmod command:
1.Symbolic mode 2.Absolute mode
Symbolic mode
The general syntax to change permission using Symbolic mode is as follows:
$ chmod <target>(+/-/=)<permission> <filename> where <permissions> can be r: read; w: write; x: execute.
<target> can be u : user; g: group; o: other; a: all
‘+’ is used for adding permission
‘-‘ is used for removing permission
‘=’ is used for setting the permission
For example, if you want to set the permission such that the user can read, write, and execute it and members of your group can read and execute it, and others may only read it.
Then the command for this will be:
$ chmod u=r w x , g=r x , o=r filename

151. What are inode and process id?

inode is the unique name given by the operating system to each file. Similarly, process id is the unique id given to each process.

152.Which are the Linux Directory Commands?

There are 5 main Directory Commands in Linux:
pwd: Displays the path of the present working directory. Syntax: $ pwd
ls: Lists all the files and directories in the present working directory. Syntax: $ ls
cd: Used to change the present working directory. Syntax: $ cd <path to new directory>
mkdir: Creates a new directory
Syntax: $ mkdir <name (and path if required) of new directory> rmdir: Deletes a directory

153. What is Virtual Desktop?

Virtual Desktop is a feature that allows users to use the desktop beyond the physical limits of the screen. Basically, Virtual Desktop creates a virtual screen to expand the limitation of the normal screen.
There are two ways Virtual Desktop can be implemented:
Switching Desktops
Oversized Desktops
Switching Desktops
In the case of Switching Desktops, you can create discrete virtual desktops to run programs. Here, each virtual desktop will behave as an individual desktop and the programs running on each of these desktops is accessible only to the users who are using that particular desktop. Oversized Desktops
Oversized Desktops do not offer a discrete virtual desktop but it allows the user to pan and scroll around the desktop that is larger in size than the physical screen.

154. Which are the different modes of vi editor?

There are 3 modes of vi editor:
Regular/Command mode: Lets you view the content
Insertion/edit mode: Lets you delete or insert content
Replacement mode: Lets you overwrite content

155. What are daemons?

A daemon is a computer program that runs as a background process to provide functions that might not be available in the base Operating System. Daemons are usually used to run services in the background without directly being in control of interactive users. The purpose of Daemons are to handle periodic requests and then forward the requests to appropriate programs for execution.

156.What are the process states in Linux?

 Ready: The process is created and is ready to run
 Running: The process is being executed
 Blocked or wait: Process is waiting for input from the user
 Terminated or Completed: Process completed execution, or was terminated by the Operating System
 Zombie: Process terminated, but the information still exists in the process table.

157. Explain grep command?

Grep stands for Global Regular Expression Print. The grep command is used to search for a text in a file by pattern matching based on regular expression.

158.Explain Process Management System Calls in Linux?

The System Calls to manage the process are:
fork () : Used to create a new process exec() : Execute a new program wait() : Wait until the process finishes execution exit() : Exit from the process
And the System Calls used to get Process ID are: getpid():- get the unique process id of the process getppid():- get the parent process unique id

159.Explain the redirection operator?

The redirection operator is used to redirect the output of a particular command as an input to another command or file.
There are two ways of using this:
‘>’ overwrites the existing content of the file or creates a new file.
‘>>’ appends the new content to the end of the file or creates a new file.
Suppose the content of the file is as follows:

160. What is a Latch?

A Latch is a temporary storage device controlled by timing signal which can either store 0 or 1. A Latch has two stable states (high-output or 1, and low-output or 0) and is mainly used to store state information. A Latch can store one bit of data as long as it is powered on.

161. What is a Microprocessor?

A Microprocessor is a device that executes instructions. It is a single-chip device that fetches the instruction from the memory, decodes it and executes it. A Microprocessor can carry out 3 basic functions :
Mathematical operations like addition, subtraction, multiplication, and division
Move data from one memory location to another
Make decisions based on conditions and jump to new different instructions based on the decision.

162 .Explain Regular Expressions and Grep?

Regular Expressions are used to search for data having a particular pattern. Some of the commands used with Regular Patterns are: tr, sed, vi and grep. Some of the common symbols used in Regular Expressions are:

163. What is the minimum number of disk partitions required to install Linux?

The minimum number of partitions required is 2.
One partition is used as the local file system where all the files are stored. This includes files of the OS, files of applications and services, and files of the user. And the other partition is used as Swap Space which acts as an extended memory for RAM.
Part B – Scenario Based Questions
Interviewers will ask scenario based questions along with theoretical questions to check how much hands-on knowledge you have. In this part of Linux Interview Questions, we will discuss such questions.

164.How to terminate a running process in Linux?

Every process has a unique process id. To terminate the process, we first need to find the process id. The ps command will list all the running processes along with the process id. And then we use the kill command to terminate the process.

165.How to find where a file is stored in Linux?

 You can use the locate command to find the path to the file.
 Suppose you want to find the locations of a file name sample.txt, then your command would be:

166. How would you schedule a task in Linux?

There are two commands to schedule tasks in Linux: cron and at.
The cron command is used to repeatedly schedule a task at a specific time. The tasks are stored in a cron file and then executed using the cron command. The cron command reads the string from this file and schedules the task. The syntax for the string to enter in the cron file is as follows:

167.Suppose you try to delete a file using the rm command and the deletion fails. What could be the possible reason?

The path specified to the file or the file name mentioned might be wrong
The user trying to delete the file might not have permissions to delete the file.

168.How do you look at the contents of a file named sample.z?

The .z extension means that the file has been compressed. To look at the contents of the compressed file, you can use the zcat command

169.How to copy files to a Floppy Disk safely?

Follow these steps to copy files to a Floppy Disk safely:
Mount the floppy disk
Copy the files
Unmount the floppy disk
If you don’t unmount the floppy disk, then the data might become corrupted.

170. What is CLI?

CLI means Command language Interpreter. It interacts with the computer program, where the user issues command in the form of text lines. It Interacts with the computer terminals also, the interface accepts the text lines and converts them as a command to the operating system.

171.What is the advantage of Open Source?

Linux was one of the first open-source technologies, many programmers added software that completely open to the users, which means you can download the file and change the code as you like. It has a wide range of options for users and increased security.

172.What is the disadvantage of Open Source?

Disadvantages of Open Source Operating System mentioned below
 Difficulty of use
 Compatibility Issues
 Liabilities and warranties
 Hidden costs

173.How many types of Shells are there in Linux?

C Shell (csh): It is like C syntax and provides spelling checking and job control.
Korn Shell (ksh): This is a high-level programming language shell.
Z Shell (Zsh): It provides some unique nature like it observes login/logout watching, file name generating, startup files, closing comments.
Bourne Again Shell (bash): It is the default to Linux distributions.
Friendly Interactive Shell (Fish): It provides web-based configuration, auto-suggestions, etc.

174. What are the basic components of Linux?

Kernel: It is the core component of Linux, it acts as an interface between software and hardware.
Shell: It acts as an interface between the user and the Kernel.
GUI: It stands for Graphic User Interface, which is another way for the user to interact with the system. But it is unlike images, buttons, text boxes for interaction.
System Utilities: These are the software functions that allow users to manage the computer.
Application Programs: Set of functions designed to perform a set of tasks.

175. What is a swap space?

Swap Space is used when then physical Ram memory is running out. It will move the Ram inactive pages to the swap space. It can consider in the form of a dedicated swap partition or swap files.

176. Yes it legal to edit Linux Kernel?

Yes. You can edit Linux Kernel because it is released under General Public License (GPL) and anyone can edit it. It comes under the category of free and open source software.

177. Define shell?

It is an interpreter in Linux.

178 . Name some shells that are commonly used in Linux?

The most commonly used shells in Linux are bash, csh, ksh, bsh.

179 .Name the Linux which is specially designed by the Sun Microsystems?

Solaris is the Linux of Sun Microsystems.

180 . Name the Linux loader?

LILO is the Linux loader.

181. Name some Linux variants?

Some of the Linux commands are:
 CentOS Ubuntu
 Redhat Debian
 Fedora

182. What is Swap Space?

Swap space is used to specify a space which is used by Linux to hold some concurrent running program temporarily. It is used when RAM does not have enough space to hold all programs that are executing.

183 . What is the basic difference between BASH and DOS?

BASH commands are case sensitive while DOS commands are not case sensitive. DOS follows a convention in naming files. In DOS, 8 character file name is followed by a dot and 3 characters for the extension. BASH doesn’t follow such convention.

184. What is CLI?

CLI stands for Command Line Interface. It is an interface that allows users to type declarative commands to instruct the computer to perform operations.

185. What is the GUI?

GUI stands for Graphical User Interface. It uses the images and the icons which are clicked by the users to communicate with the system. It is more attractive and user-friendly because of the use of the images and icons.

186 . Which popular office suite is available free for both Microsoft and Linux?

Open Office Suite is available free for both Microsoft and Linux. You can install it on both of them.

187. What is SMTP?

SMTP stands for Simple Mail Transfer Protocol. It is an internet standard for mail transmission.

188 .What are the basic commands for user management?

last, chage,  chsh,  lsof,  chown,  chmod,  useradd, userdel,  newusers etc.

189. What is the maximum length for a filename in Linux?

255 characters.

190 . Is Linux Operating system virus free?

No, There is no operating system till date that is virus free, but Linux is known to have less number of viruses.

191 . Which command is used to uncompress gzip files?

gunzip command is used to uncompress gzip files.

192.Why do developers use MD5 options on passwords?

MD5 is an encryption method, so it is used to encrypt the passwords before saving.

193. What is a virtual desktop?

The virtual desktop is used as an alternative to minimizing and maximizing different windows on the current desktop. Virtual desktop facilitates you to open one or more programs on a clean slate rather than minimizing or restoring all the needed programs.

194.What is the difference between soft and hard mounting points?

In the soft mount, if the client fails to connect the server, it gives an error report and closes the connection whereas in the hard mount, if the client fails to access the server, the connection hangs; and once the system is up, it again accesses the server.

195 .Does the Alt+Ctrl+Del key combination work in Linux?

Yes, it works like windows.

196 .What are the file permissions in Linux?

There are 3 types of permissions in Linux OS that are given below:
 Read: User can read the file and list the directory.
 Write: User can write new files in the directory .
 Execute: User can access and run the file in a directory.

197 . What are the modes used in VI editor?

There are 3 types of modes in vi Editor:
a. Regular mode or command mode
b. Insertion mode or edit mode
c. Replacement mode or Ex-mode

198. How to exit from vi editors?

The following commands are used to exit from vi editors.
:wq saves the current work and exits the VI. :q! exits the VI without saving current work.

199 .How to delete information from a file in vi?

The following commands are used to delete information from vi editors.
 x deletes a current character.
 dd deletes the current line.

200 . How to create a new file or modify an existing file in vi?