Computer Booting

Abstract

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• When the power is switched on, BIOS is executed first, followed by Boot Device, lastly Kernel Booting

BIOS

• The first program that starts when booting up a computer

  1. Checks Main Memory capacity
  2. Check IO Device
  3. Scanning PCI Bus etc to detect all devices attached
  4. Determine the Boot Device by trying out a list of devices stored in the CMOS
  5. The Boot loader inside the boot device will carry out the next step
     

• Contains low-level IO software

• Nowadays, stored in Flash RAM - nonvolatile & can be updated

• The newer standard is called UEFI

Boot Device

• Storage device that contains Master Boot Record and the OS
• Master Boot Record is read into Main Memory to start the Boot Loader

Boot loader

1. Examines the partition table at the end of boot sector to determine which partition is active. Providing a menu for user to select which OS to boot
2. Loads in the Kernel into the Main Memory
3. Kernel Booting will finish up on the booting of the OS
   

• Common boot loaders are Grub2

References

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• How Does Linux Boot Process Work?