Linux System Booting Process Sequence


1)When we switch on Linux system BIOS it will take the control of the system.
2)BIOS Perform some system integrity test(POST-Power on Self test).For then search and load MBR in the 1st sector of the boot able disk(boot able disk depends on the booting priority)
3)MBR less than 512 bytes
a)Primary boot loader info into 1st 446 bytes
b)Partition info for next 64 bytes.
c)mbr validation check in last 2 bytes. Totally 446+64+2=512 bytes.
4)This MBR load or execute the Grub boot loader
(grub.conf contain 6 lines -1.default-2.timeout-3.IMAGE-4.TITLE-5.root-6.kenrel-7.initrd) .
5)kernel execute /sbin/init program,1st program execute by Linux kernel.
6)initrd temporary file system contain necessary drivers compile inside, which helps to access hard drive partition and other hardware.
7)read /etc/inittab run the default run level.
8)S12syslog, S80senmail. Program or service start according to their run level.

Note : If we did not get any display after the BIOS POST test, then the problem in Hard disk MBR (partition table)

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