->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.
->TYPES OF FILES
- Regular File or General File – text, image, video, ascii code, binary code, etc.
- Directing File – It is the container which contains other file types.
- Device File – In linux, device is also representation of file.
Author: Ravi Chandra Pathi
Source: https://secinfos.in/2020/04/24/linux-concepts/