History

  • Linux operating system is launched in 1991 as a personal project by Finnish student ‘Linus Torvalds‘ while studying computer science at University of Helsinki.
  • Initially it was called ‘Freax’ for early six months of its development.

Introduction

  • Linux started out as a Unix variant with one major difference-its source code was freely available under the auspices of Free Software Foundation (FSF). Due to this, it quickly positioned itself as an alternative to other Unix workstations.

Features

There are several strong features of UNIX/Linux. These are – 

(i) Portability

    • Linux OS shows portability i.e. this OS could be run on different machines easily, because of its design/architecture, with no/little modifications on the machines using C compiler.
    • It has a very small portion that is dependent on hardware so only those parts needs to be modified during installation on different machines.

(ii) Inexpensive

    • All versions of Linux is freely available for downloaded from its website. If we don’t want to download, pre-packaged versions of Linux may be purchased online.
    • In addition, the downloaded software may be legally shared with the friends.
    • In addition, during up gradation of the operating system in future, the Linux upgrade would be free.
    • In addition to being inexpensive, Linux can be run on the old system as well such as Intel 386 microprocessors.

(iii) Multitasking

    • Linux system allows to invoke more than one job from the same terminal simultaneously.
    • The running multiple tasks may be background running or  foreground running or both with different priority. Normally, foreground jobs have high priority and background jobs have  low priority.

(iv) Fast

    • Linux runs well on old computers, and  is even faster on newer powerful computers. This is because Linux programs are very efficient and lean. They use few resources as possible during its processing.
    • Unlike Windows, Linux programs use little graphics, if any.
    • It is said that Linux may not be pretty, but it is fast.

(v) Multiuser

    • Linux system allows a group of users to use the same system/computer simultaneously having multiple terminals each connected with single/multiple powerful system (server). Here, each user has different access rights 
    • This structure exists in client server mode normally. 

(vi) Stable

    • Since the Linux code is well written and hence increases the speed at which Linux runs and improves the stability of the operating system.
    • Linux is said to be impossible to crash. If an application crashes, we can simply remove the program from memory to restart the computer. This is one of the reasons Linux is used on many web servers where stability is crucial. With Linux, web-hosting providers can guarantee 99.9 percent uptime.

(vii) Security

    • Linux is considered as the most secure OS because it’s highly configurable as per need.
    • Linux uses the core security model i.e. a form of Discretionary Access Control (DAC). This security features of the Linux kernel have evolved significantly to meet modern requirements.
    • Linux provides a high degree of security, this is due to it provides several layer of security as per requirements i.e. user level, admin level, group level and domain level.
    • Due to several layer of security, Linux prevents unauthorized people from gaining access to the system.
    • Anti-virus software can exist/install for Linux, but we normally probably don’t need to use it. Viruses that affect Linux are still very rare. It is believed that Linux is not as widely used as other operating systems in an organisation, so no one creates viruses for it.
    • Linux scans malwares on mail servers, web servers and file servers, as well as endpoints.

(viii) Piping Facility

    • A pipe is a form of redirection in Linux where output of one process is used as input of another process. To complete this process, sending the output and connecting to the input process is done by piping technique for further processing.
    • Linux provides piping facility in which one program can be connected with others.

(ix) Open Source

    • As we know that, Linux is open-source software i.e. the users can read the source code and modify it as per requirements.
    • However, during development, “beta” releases of the kernel are available to developers who will download the code and test it thoroughly. When possible, they will find any problem and correct the code. This process helps to ensure that the final release of the kernel/OS is as well written as possible.

(x) Communication

    • Linux provides the communication facility in which one computer user may communicate/share with other connected users/computer/terminals for transferring data/outputs/messages.

(xi) Portable Application Programs

    • Linux have the ability to hides the machine architecture from the users making it easier to write programs that runs on different hardware implementations easily. Thus, this program became portable for another hardware.

Advantages

  • Open Source Availability.
  • Free to use.
  • Various version/distribution/customization available to fulfill different needs.
  • Linux OS’s have almost negligible vulnerability to viruses and malware.
  • There is no such thing as ‘drivers’ for hardware on Linux.
  • Most of the paid application software for Windows available for free on Linux.
  • Linux consumes very few resources during processing, so the computer hardware need not have high-end specification.
  • It can run many Windows apps using emulators.
  • It is very stable, almost no crashes.
  • It can even be run alongside Windows or inside Windows using virtual software-Virtual Box.
  • Linux is very reliable/flexible because it is installed in non-partitioned area of the memory.
  • It is said that Linux can breathe new life into old computers.
  • Linux comes in all sizes and flavors, which offers a wide variety from which will best suit our needs.

Disadvantages

(i) Lack of Support

    • Support and documentation for Linux can be spotty at best i.e. A customer who downloads Linux from a server/websites may receive only an electronic manual and access to online help pages. They do not have extensive documentation and support like Microsoft products. Also,  they do not release service pack and updates frequently to fix discovered/coming vulnerabilities like Microsoft products .

(ii) Security

    • Because Linux is Open Source hence its source code is distributed with the Linux software, programmers are free to explore how the system works, for good or bad/sense. Many security loopholes can be searched/identified/reported in the literature. This may lead into major security loopholes.

(iii) Limited Software Selection Choice

    • Unlike Microsoft Products, Linux users, at present, have limited availability/choices of updated software in every category. 
    • As time passes, Linux products are also available in the market as per most demanded.

(iv) Limited Hardware Support

    • As we know that, not all popular software run on Linux, not all hardware products work with Linux.
    • Linux vendors work very hard to support the more common devices. They provide drivers for hardware devices.
    • Many branded companies still have not written a Linux compatible driver.

(v) Complexity

  • For a beginning user, Linux can be frightening to use; entering the wrong command can have serious consequences.
  • It doesn’t help that Linux is also case sensitive, so we must enter the commands in lowercase, and be careful to use the correct case for each sub-command we use with a command. Upper and lowercase are often different actions.

Use

  • Unix and Linux operating systems are widely used on corporate servers, web sites, and large-scale networking environments.
  • Due to high quality designing of its kernel qualities such as stability, modularity and easy configurability-it is now dominating the corporate world significantly in use.
  • we still know many people who use it on their desktop computers or workstations at home.

Requirements of Linux Installation 

Linux File System 

A Linux file system consists of –

BOOT BLOCK

    • It is one of the major components of a Linux file system.
    • This component is located in the first few sectors of a Linux file system.
    • The boot block contains the initial bootstrap program which is used to load the operating system during loading process.

SUPER BLOCK

    • It is another major components of a Linux file system.
    • A super block describes the state of the file system i.e. it includes the total size of the partition, the block size, pointers to a list of free blocks, the inode number of the root directory, magic number, etc.

INODE TABLE

    • inodes‘ stands for index nodes.
    • inode table is mainly used to handle different type of Linux file.
    • inode is a tabular structure, as a linear array form, which contains various important information regarding Linux file process. These are –
      • file ownership information.
      • file type/Nature of file (such as regular, directory, special device, pipes, etc.).
      • file access permissions.
      • time of last access, last modification etc.
      • number of links (aliases) to the file.
      • pointers associated to the data blocks for the file.
      • size of the file in bytes (for regular files).
      • major and minor device numbers for special devices.
    • An inode is identified by its inode number, which contains the information needed to find the inode itself on the disk.

DATA BLOCKS

    • Data blocks contains the actual contents/data of files.
    • The Linux file system allocates data blocks one at a time from a pool of free blocks.

STANDARD DIRECTORIES

    • The directory structure and directory contents in Linux are defined by a body called ‘The File system Hierarchy Standard (FHS).
    • The directory structure and directory contents are maintained by the Linux Foundation.
    • According to FHS, all files and directories appear/included under the root directory( /), even if they are stored on different physical drives or virtual devices.
    • Linux contains several directories which contains many Linux files and having different unique functions. Some important standard directories are – root directory(/), bin directory(/bin), dev directory(/dev), boot directory(/boot), etc directory(/etc), lib directory(/lib), home directory(/home), media directory(/media), opt directory(/opt), tmp directory(/tmp), sys directory(/sys), usr directory(/usr), var directory(/var) etc.

Architecture of Linux

  • A typical Linux consists of primarily following components: -Hardware, Kernel, Shell and Utilities (and layer of Users)

Hardware:

    • Peripheral devices such as RAM, HDD, CPU and other related several components together constitute Hardware layer for the Linux operating system.
    • The innermost layer of the Linux.
    • They are responsible for processing of given instructions.

Kernel:

    • The Core/main part of the Linux OS is called Kernel.
    • It is responsible for doing almost all activities of the Linux operating system. These are –
      • It interacts directly with hardware to complete the given instructions.
      • There may be two types of kernels – Monolithic Kernel and Micro Kernel.

Shell:

    • The shell is an interface between the user and the kernel.
    • It hides the complexity of functions of the kernel from the user.
    • It accepts commands from the user and performs the action.

Utilities:

    • Operating system functions are granted to the user from the Utilities.
    • Individual and specialized functions are can be utilized from the System utilities.

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Categories: Unix/Linux OS

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