Linux Interview Questions

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Linux is an operating system based on UNIX and was first introduced by Linus Torvalds. Popularity of Linux is due to It is free and opensource. The OS can be customized as per our requirements. It is very robust and adaptable. It has Immense amount of libraries and utilities. It is based on the Linux Kernel and can run on different hardware platforms manufactured by Intel, HP, IBM, SPARC, MIPS and Motorola. Another popular element in Linux is its mascot, a penguin figure named Tux.

On the other hand, Unix originally began as a propriety operating system from Bell Laboratories, which later on spawned into different commercial versions. Most of the more popular UNIX flavors focus on high-performance hardware, usually of a proprietary nature, or using high-end standard computing architectures, like SPARC.

What is the difference between UNIX and LINUX?

Linux and UNIX are very similar. Linux was started by a university student (Linus Torvalds) without any initial support from any large organization. Linux also began as in mimicry of other well- known UNIX-like implementations, whereas the initial UNIX implementations were original research. Linux is free, open source and intended as a non-propriety operating system for the masses. Although Linux runs on many kinds of equipment, it is well known for its support of commodity Intel PC-based hardware.

Linux follows the Free Software Foundation’s radical licensing model, that implies a great deal of liberty to those that interact with Linux technology. UNIX versions provided by other vendors have profit strategies embedded in them. People who offer Linux services might have a profit strategy, but Linux itself doesn’t. This means that vendor lock-in is less of an issue with Linux than it is with other UNIX offerings.

What is BASH?

BASH is short for Bourne Again SHell. Bash is an application. It was written by Steve Bourne as a replacement to the original Bourne Shell (represented by /bin/sh). Bash is just an application, and its primary job is to run other applications (in the form of commands) that are installed on the same system. When you start a terminal (such as the GNOME Terminal or Konsole on Linux or iTerm2 on macOS) running the Bash shell, you’re greeted with a prompt. A prompt is a symbol, usually a dollar sign ($), indicating that the shell is waiting for your input. One reason Bash (and Linux in general) is considered so powerful is because it’s scriptable. Anything you can type into Bash manually, you can also list in a plain-text file and have Bash run it for you. 

It has since been adapted as the default shell for most systems running Linux. They do this because Bash is well-known, and it has several convenience functions that other shells don’t. However, some systems use another shell by default. To find out whether you’re running a Bash shell, you can use the echo command along with a special variable representing the name of the currently running process:

echo $0
bash

What is Linux Kernel?

The Linux® kernel is the main component of a Linux operating system (OS) and is the core interface between a computer’s hardware and its processes. It communicates between the 2, managing resources as efficiently as possible. It is also used to provide an interface for user-level interaction.

The kernel has 4 jobs:

  1. Memory management: Keep track of how much memory is used to store what, and where
  2. Process management: Determine which processes can use the central processing unit (CPU), when, and for how long
  3. Device drivers: Act as mediator/interpreter between the hardware and processes
  4. System calls and security: Receive requests for service from the processes

What is the importance of the GNU project?

The GNU Project is a free software, mass collaboration project that Richard Stallman announced on September 27, 1983. It also allows you to redistribute copies of software to other people, as well as the freedom to improve software and have it released for the public.

What is the advantage of open source?

Open source allows you to distribute your software, including source codes freely to anyone who is interested. Lower license fees, development in-house or by freely choosable IT service providers. This eventually benefits everyone in the community. It’s an open-source world: ​78 percent of companies run open-source software. The good news is that open-source software is used in the vast majority of businesses.

What are the basic components of Linux?

Linux System components
Linux System components

Just like any other typical operating system, Linux has all of these components: kernel, shells and GUIs, system utilities, and an application program.

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. Each Linux distribution comes with a single default desktop environment chosen from the many different desktop environments available for Linux. But you don’t have to stick with the default. Switching desktop environments is as simple as installing a software package and selecting your preferred environment on the login screen, known as a display manager. You don’t have to install an entirely different Linux distribution. Installing another DE can change system files and dependencies, alter default system and application settings, and create incompatibilities. 

What is the basic difference between BASH and DOS?

        
DOS is single process, it can only execute one        thing at a time        
        
Linux is multi-process, it can runs a multitude of        process at the same time and possess mechanism to share CPU time and        everything that come with the complexity to run multiple processes on        the same system. (which is quite lambda now a day).        
        
DOS is single user, it can only allow one        user at a time and doesn’t offer any security or authentication        mechanism on its own.        
        
Linux is multi user, it can allow many users to share        the same system and to authenticate them and offer security mechanism to        isolate object owned by one user. (Windows also is multi user). But        Linux allow more than one user to be connected at the same time on the        same system. This feature arrived much later under Windows (But cannot        remember exactly with which version).        
        
DOS can only support 1 CPU and 640 KB of RAM        (note KiloBytes not MegaBytes), and 64MB when using extended memory        (basically using the 640Kb as an index of memory address that allow to        map up to 64MB of RAM addresses).        
        
Linux can support up to 384 CPU, 12T RAM        
        
DOS doesn’t support natively networking. But it can        be add by running application inside DOS (which at this step i’m not too        sure how since it is a mono process OS)        
        
Linux is being used as the OS for Network        router like Juniper who run the Internet.        
Linux vs DOS

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