Linux boot process Linux kernal Linux rootfs File systems

1. CONTENTS
 Linux boot process
 Linux kernal
 Linux rootfs
 File systems
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2. Linux boot process

3.  What is Booting?
 Booting is basically the process of starting the computer.
 It is a short form of bootstrapping.
 Bootstrapping usually refers to a self-starting
process that is supposed to proceed without
external input that is when the power
button is pressed CPU
starts its own process without
any human interference.
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5. BIOS
 It is an initial test performed by the BIOS.
 POST (Power On Self Test).
 If any error occurs, the system produces a beep
sound.
 Loading MBR to RAM
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6. MBR/EFI
BIOS assume that the boot device(hard disk/ SSD) start with the record called Master Boot
Record(MBR).
How BIOS see the the hard disk
MBR consists of 512 or more bytes located at the very beginning sector of the bootable device.
Boot block read the partitioning information from the MBR and identifies the disk partition marked as active and then
executes the second stage boot loader.
Below is a simplified structure of the MBR:
Bootsrap code : 446 bytes
partition table : 64 bytes
Boot signature : 2 bytes
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8. GRUB/LILO
 If we have multiple kernal images installed on your system ,you
can choose which one to be executed.

 Each operating system has its own bootloaders.
 For example, GNU GRUB, LILO (Linux Loader), and rEFInd.
 Main job is to load kernal and init image into memory.

9. Kernal
 Initiate the kernel, the operating system now controls access to our
computer resources.
 Linux kernel follows a predefined procedure:
 decompress itself in place
 perform hardware checks
 gain access to vital peripheral hardware
 run the init process
 kernel initiates the init process, which starts the parent process.
 the parent of all Linux processes is “Systemd”
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10. Linux Kernel
Core interface between a computer’s hardware and its processes.

11. Linux Kernel
Linux is kernel created in 1991 by Linus Torvalds
It’s been in constant development since then and is
now at version 6.2.0-36.
Its used in desktop,laptop,smartphones,servers and
Many other devices.
Free & Open Source : No need to pay
fast
Secure : Monolithic Kernel design
Scalability : From phones to super-computers
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12. What is a Kernel ?
A computer needs both software and hardware to do
anything
There has to be a layer of softerware that operates
hardware at low lavel
It is the portion of the operating system code that is always
resident in memory and facilitates interactions between
hardware and software components
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13. Kernel
A kernel is the core of the operating system
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14. How does a kernel work?
The kernel responds to system calls ;
These are called by different parts of the operating system to get
The actual physical hardware to do things
For example, whenever you copile and run c code C library
uses system calls
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15. What actualy kernel manages?
 Random-access memory
 Input/output devices
 Memory management
 Device management
 Process management
 System calls
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16. Linux file-system
The Linux file system structure is a hierarchical arrangement of directories and files that defines
how data is organized and accessed in a Linux-based operating system.

17. Contents
of
rootfs
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18. file-system
A file system is a set of processes that controls how, where and when
data is stored and retrieved from a storage device.

19. Filesystem
 structural way to store and access our files from the system
storage
 various types of filesystems:
 Ext (Extended Filesystem), Ext2, Ext3, Ext4
 JFS (Journaling Filesystem)
 Vfat
 Ubifs.
 tmpfs.
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