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)
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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