Introduction of the start-up process

Start-up process:

There are bios and CMOS two things in the computer, CMOS is a storage device that records various hardware parameters and is embedded in the motherboard, and the BIOS is a firmware written to the motherboard (firmware is a software program written to the hardware). This BIOS is the first program that the computer system will actively run when it starts up!

The BIOS can set up the hardware devices in the computer, we take the hard disk as an example, the BIOS will be based on the user's configuration to obtain a bootable hard disk, and to the hard disk to read the first magnetic region of the MBR location. MBR occupies 446bytes of hard disk capacity, where the boot loader is placed, and the next step is the work of the boot loader inside the MBR.

The purpose of the bootloader is to load the kernel file, because the bootloader is provided by the operating system at the time of installation, so it knows the file system format on the hard disk, so it can read the kernel file, and then the kernel file works, the operating system will be launched successfully!

Process Brief:
BIOS ==> MBR ==> boot loader ==> kernel file


1, BIOS: Start the active firmware, will know the first bootable device.

2, MBR (Master boot Record): The first bootable device in the first magnetic region of the main boot record block, including the startup management program.

3. Boot Manager (boot loader): Software that can read core files to run, Grub (for Linux) is the most mainstream boot loader.

4. Core file: Start the function of the operating system.

The MBR is located in the main boot sector (i.e., the first sector of the 0 Head 0 cylinders), with a total of 446bytes.

Both the BIOS and MBR are features that the hardware itself will support, and boot loader is a set of software installed on the MBR or partition boot sector of the operating system.

Boot Loader's main tasks:

1, provide the menu: the user can choose different boot options, this is also a multi-boot important function!

2. Load the core file: Start the operating system by pointing directly to the bootable program section.

3, transfer to other loader: Transfer the boot load function to other loader responsible.

The boot loader is installed on the boot sector to enable multi-boot functionality.


The properties of the Boot loader:


1, each partition has its own boot sector (boot sector)

2, the actual bootable kernel files are placed in each partition.

3. Boot loader will only know the bootable kernel files within the system partition, as well as other boot loader.


If you want to install multi-boot, it's a good idea to install Windows before installing Linux (of course, Daniel can still do so, you can install the boot loader that recognizes Windows/linux)


Linux in the installation, you can choose to install boot loader in the MBR or partition of the boot sector, and the boot loader Linux can manually configure the menu, so you can in the Linux boot loader to join the Windows boot option.

When Windows installs, his installer will proactively overwrite the boot sector of the MBR and its own partition, and it does not allow us to choose the function of the menu.

Related reading:

Linux boot boot process grub and MBR http://www.linuxidc.com/Linux/2013-07/87923.htm

Basic Linux Disk Concepts (disk, partition, MBR, GPT) http://www.linuxidc.com/Linux/2013-06/85717.htm

rhce_rhel6_124 U20.3 Solve grub problem, fix MBR http://www.linuxidc.com/Linux/2012-10/71871.htm

Some questions about MBR, Grub http://www.linuxidc.com/Linux/2011-07/39075.htm

Ubuntu update causes MBR damage misoperation lost partition table http://www.linuxidc.com/Linux/2010-08/28043.htm

This article is from the Linux commune website (www.linuxidc.com) Source Link: http://www.linuxidc.com/Linux/2013-09/90295.htm

Introduction of the start-up process