What is computer booting?
Process of bringing up the operating system for users is called computer boot.
This is a simple classification. But behind this word called computer boot, there are sequence of activities done by your computer.
Following is booting process of Linux operating systems.
What happen when you press the power button of your computer?
After pressing power button, first of all power is going to power unit of your machine. Then power unit provide amount of power need by each device in mother board and sends a signal to BIOS (Basic Input Output System) chip in mother board. Then BIOS chip starts a process called POST (Power On Self Test). Under this POST process BIOS chip,
If BIOS found boot loader in external memory, first sector or first 512 bytes of that external memory device loaded in to the main memory(RAM) as first instruction of the boot loader is in 0x7C00 memory address in RAM.
After loading boot loader in to the RAM , address of the first instruction(0x7C00) of boot loader send to PC(Program Counter). Then CPU will execute the boot loader. When boot loader running, it search for the Kernal inside the hard disk. If it is found, then it will loaded in to the RAM and address of first instruction of the kernal send to PC. Then CPU will start execution of the Kernal.
Then kernal load user program called "INIT" and hands over the machine to the user. INIT is the parent process of all the other processes.
INIT process' first job is to make sure your disks are working normally. Then INIT will start several deamons. Deamons are some programs. As a first deamon, INIT will start a program called "GETTY". This program will prepare the machine for users. Nowadays INIT will start several copies of "GETTY"(7 or 8). Therefore you have several virtual consoles. Then INIT will start several deamons like networking and other services.
The most important deamon is xserver. xserver program will manage your display, key board and mouse. Also xservers' main job is to produce color pixel graphics which you normally see on your screen. Last part of the boot process is graphical login. That produces by a program called "Display Manager".
Process of bringing up the operating system for users is called computer boot.
This is a simple classification. But behind this word called computer boot, there are sequence of activities done by your computer.
Following is booting process of Linux operating systems.
What happen when you press the power button of your computer?
After pressing power button, first of all power is going to power unit of your machine. Then power unit provide amount of power need by each device in mother board and sends a signal to BIOS (Basic Input Output System) chip in mother board. Then BIOS chip starts a process called POST (Power On Self Test). Under this POST process BIOS chip,
- Check whether all the devices receives right amount of power and memory is corrupted.
- Then check boot order and according to the boot order find boot loader.
If BIOS found boot loader in external memory, first sector or first 512 bytes of that external memory device loaded in to the main memory(RAM) as first instruction of the boot loader is in 0x7C00 memory address in RAM.
After loading boot loader in to the RAM , address of the first instruction(0x7C00) of boot loader send to PC(Program Counter). Then CPU will execute the boot loader. When boot loader running, it search for the Kernal inside the hard disk. If it is found, then it will loaded in to the RAM and address of first instruction of the kernal send to PC. Then CPU will start execution of the Kernal.
Then kernal load user program called "INIT" and hands over the machine to the user. INIT is the parent process of all the other processes.
INIT process' first job is to make sure your disks are working normally. Then INIT will start several deamons. Deamons are some programs. As a first deamon, INIT will start a program called "GETTY". This program will prepare the machine for users. Nowadays INIT will start several copies of "GETTY"(7 or 8). Therefore you have several virtual consoles. Then INIT will start several deamons like networking and other services.
The most important deamon is xserver. xserver program will manage your display, key board and mouse. Also xservers' main job is to produce color pixel graphics which you normally see on your screen. Last part of the boot process is graphical login. That produces by a program called "Display Manager".
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