Embedded Files
After power ON
power on ---------------->
SMPS
Motherboard
Processor
Bios (ROM CHIP)
POST (power on self test)
(First it detect disply)
Post bring first boot device in kernel.
A.C power connector with 4 pin.
+12 V (for motors)
-12 V (ports Like monitor, serial extra )
+5 V (I.C)
-5 V (Refresh the RAM)
ROM
Bios : software and firmware manufacturer of M/B puts
BIOS in Rom chip Rom get deposited in RAM
Now,Ram is play ground BIOS start playing , bios
Comes from ROM CPU sends BIOS to RAM, BIOS wants to
Load OS but Doesn’t know which OS to load then BIOS Learns.
CMOS: It comes with M/B and has program in it we can make Changes in CMOS Data, which is inside it press DEL Key to change the settings of CMOS.
Bios load the Cmos in Ram ,Ram consist of Cmos+BIOS
Cmos as why have you called me.
Bios : to load OS.
Cmos : who asked.
Bios : CPU & I want to load OS.
CMOS : which OS
BIOS : Any
CMOS : OK, Go to 1st boot Device
In First boot device it look for MBR ( Master boot Record )
MBR is located at cylinder 0 ,head 0 ,sector 1
MBR = 512 bytes
1)boot sector = 446 bytes
2)partition Table = 64 bytes
3)Magic NO = 2 bytes
in boot sector existing files ntdlr , CHS value , grub binary.
Disk geometry exist with Partition Table
GRUB
Ground unify boot loader
After MBR comes in RAM it will execute boot loader binary from boot
Sector.
If magic NO is ok it will load OS
If there are multi OS
Grub send 13 H interbred when ntdlr start executing and task
Control to him self In the system BIOS checks the system and
Launches the first stage boot loader.
The first stage boot loader load itself into the memory and
Launches the second stage boot loader from the first boot
Partition.
The fist stage boot loader is small machine code binary on the MBR
It’s sole job is to locate the second stage boot loader and load
The first into the memory.
Once the second stage boot loader is in the RAM it present the
User with Graphical screen showing different OS and kernel it
Has been configured to boot the graphical screen comes because
Of.
/boot/grub/grub.conf
or
/etc/grub.conf
After selecting OS (LINUX) when the kernel is located it
Immediately initialize and configure the computer memory and
Various hardware attach to PC including all processor input output
Sub system and storage devices it looks for compress init RAM_FS
Image in pre determine location in memory it uncompress it
Directory to /sysroot to load all necessary drivers.
After this init co-ordinate the rest of the boot process and
Configure enviourment of users.
When the init program start it become parent and grand parent
Of all other process and all process start automatically.
#ps –a |less
(to know the all process and ID then it first Runs also)
/etc/rc.d/rc.sysinit
which state the enviourment path, swap checks the file system
execute all there steps requirement for system initialization.
/etc/init.d/functions
Then the init command start /etc/inittab which describe how
System should be setup in each Run level.
(from any file put #for particular line To comment the line)
NOTE: Linux system can has 11 terminals configured.
The init start all the background process by looking appropriate
RC directory for the run level specified as a default in
/etc/inittab file.
When booting to run level 5 the init program looks in
/etc/rc.d/rc.5.d
last script is /etc/rc.local mingetty lords drivers for
Terminals from /etc/issue
Login prompt is because of /bin/login , then login name
checked in /etc/passwd and the password check in authorization
in /etc/shadow .
Then login file goes in sleep state until you go in different
Terminals when login goes sleep state mingetty comes into the
Action and then /etc/motd send mal for user read.
# vi /etc/motd (If we want to add some banner after login. we can
add text in this file.
#stty –echo
(TO do not appear typed command )
#stty echo
(To enable in previous display command)
THAT WAS TOTAL FILES OF USE IN BOOTING PROCESS.
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