The Boot Process of x8.6 REHL and Fedora Linux System

The Boot Process Of x86 system REHL and Fedora Linux

Step1:- Press button Power then Post run (Power on self test) .
The POST is a built-in diagnostic program that checks your hardware to ensure that everything is present and functioning properly (check min memory for boot ,keyboard,other devices).If there is no error found it goes to Step2 otherwise give any Beep error.

Step2:- Now BIOS transfers control for MBR .It checks primary hard disk and active partition.

Step3:- The first stage boot loader GRUB or LILO loads itself into memory and launches the second stage boot loader from the /boot/ partition.

Step4:-The second stage boot loader loads the kernel into memory, which in turn loads any necessary modules and mounts the root partition read-only.(The boot loader then places the appropriate initial RAM disk image, called an initrd, into memory. The initrd is used by the kernel to load drivers necessary to boot the system. This is particularly important if SCSI hard drives are present or if the systems uses the ext3 file system)

Step5:- The kernel transfers control of the boot process to the /sbin/init program.

Step6:- The /sbin/init program loads /etc/rc.d/rc.sysinit scrip , /etc/sysconfig/clock.The init command then runs the /etc/inittab script.the init command sets the source function library, /etc/rc.d/init.d/functions.Now checks /etc/inittab file.Default runlevel is 5 in RedLinux and fedora.It checks runlevel their scripts (/etc/rc.d/rc5.d/) then at last things the init program executes is the /etc/rc.d/rc.local file. load and all services and user-space tools, and runlevel 5, the /etc/inittab runs a script called /etc/X11/prefdm. The prefdm script executes the preferred X display manager — gdm, kdm, or xdm, depending on the contents of the /etc/sysconfig/desktop file mounts all partitions listed in /etc/fstab.

Step7:-Now user get login screen.