Linux & Concepts

->What Is Linux?

Linux is an open source Operating System.Actually is a kernel.Which clubs with X_windows to make it Operating Systems.An operating system kernel first released on September 17, 1991, by Linus Torvalds.

->What Is Operating System?

It is system which boot or loads the system.

->What Is KERNEL?

It is a interface between hardware & software.

->Types Of Linux Distribution’s

  • Red-hat
  • Fedora
  • Cent-OS
  • SUSE
  • Debian
  • Kali Linux
  • Ubuntu
  • Linux Mint, etc.

->Boot Process

  • BIOS – Basic Input Output System
  • MBR – Master Boot Record
  • GRUB – Grand United Boot Loader
  • KERNEL
  • INIT
  • RUN-LEVEL

->BIOS

  • Power On Self Test (POST).
  • Perform Sum Integrity Checks.
  • Loads & Executes the boot loader program.
  • It looks for boot loader programs during BIOS startup to check the sequence of operating system.
  • Once the boot loader program is loaded, control pass to boot loader program (Master Boot Record).

->MBR

  • It is located in the first sector of the hard-disk i.e /dev/sda.
  • MBR is less than 512 bytes sign
  • Primary boot loader program information contain 446 bytes in size.
  • Partition table into 64 bytes.
  • MBR validation check in 2 bytes.
  • It contains the information of GRUB.

->GRUB

  • If you have installed multiple kernel images on your system.Then with the help of GRUB you can choose one  kernel image.
  • GRUB have the knowledge of file system.
  • GRUB is stored on /boot/GRUB/grub.conf

->KERNEL

  • It loads or mounts the root file system.
  • Kernel executes /sbin/init program.
  • INITRD stands for Initial RAM Disk.
  • Initial RAM Disk Program is used by the kernel for temporary use until kernel is loaded and root file system is mounted.It will also check the hard-disk partition.

->INIT

  • Init file located in the /etc/inittab file to decide run level.
  • Init 0 – halt
  • Init 1 – Simple user mode
  • Init 2 – Multi user without NFS
  • Init 3 – Multi use
  • Init 4 – Unused
  • Init 5 – X11
  • Init 6 – Reboot

->FILE SYSTEM

Everything is file in linux. The file are a order in a free structure.

linux

->TYPES OF FILES

  1. Regular File or General File – text, image, video, ascii code, binary code, etc.
  2. Directing File – It is the container which contains other file types.
  3. Device File – In linux, device is also representation of file.

Author: Ravi Chandra Pathi

Source: https://secinfos.in/2020/04/24/linux-concepts/

 

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