1)Bios
It BIOS loads and execute the first 512 bytes off the disk which is called ad MBR.
MBR ( Master Boot Record) called as frist stage boot Loader. It searches for the 2nd
boot Loader
2) GRUB
Its a 2nd Boot stage loader.Its contain kernel & initrd image.
3) Kernel
initialise devices
mounts root filesystem
kernel prints: VFS: Mounted root (ext2 filesystem) readonly
runs /sbin/init which is process number 1
4) Initrd
loads ram disk image
kernel runs /linuxrc (this allows you to boot a small modularized kernel and to load the few drivers that are really needed as modules)
* load modules
* initialise devices
* /linuxrc exits
"real" root is mounted
kernel runs /sbin/init
5) /sbin/init
reads /etc/inittab
redhat: /etc/rc.d/rc.sysinit script which: loads modules, check root FS and mount RW, mount local FS, setup network, and mount remote FS
switches to default runlevel eg 3.
* run scripts /etc/rc3.d/S*
* run programs specified in /etc/inittab
6) Run Level
Scripts in /etc/rc*.d/* are symlinks to /etc/init.d
* Scripts prefixed with S will be started when the runlevel is entered,
* Scripts prefixed with K will be killed when the runlevel is entered,
7) Finaly We get boot Prompt
