Linux Questions And Answers Pdf

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Linux is a Unix-like open-source computer operating system (OS) that directly manages hardware and resources of a system such as CPU, memory, and storage, and manages the communication between software and hardware. It was first released on 5 October 1991 by Linus Torvalds for computers and is considered more secure and faster than Windows. It is freely distributable and is generally built around Linux Kernel (low-level system software that is used to manage hardware resources for users). Furthermore, it can be installed in mobiles, laptops, computers, notebooks, etc. Flavors of Linux OS include Ubuntu, Debian, SUSE Linux, Gentoo, etc.

Enhance your chances of performing well in the interviews with our comprehensive guide, which covers important topics on Linux to help freshers, as well as experienced candidates, ace their interviews.

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.

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.

LILO (Linux Loader) is basically a bootloader 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 bootloader i.e., LILO for it as it allows fast boot of Linux OS.

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.

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.

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.

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.

Cron: It is a program in Linux that is used to execute tasks at a scheduled time. It works effectively on machines that run continuously.

Anacron: 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.

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.

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.

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.

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.

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.

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:

/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.

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.

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.

Umask, 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, umask 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: umask [-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 umask command thus allowing it to be copied and pasted as a future input.

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.

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.

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