Lec. 16 The Boot Process

Boot Process Overview
• Four main stages • Some stages can be modified by administrators
Firmware Stage • Firmware is referred to as the BIOS (Basic Input Output System) • UEFI (Unified Extensible Firmware Interface) has replaced the BIOS on some systems but typically still referred to as “BIOS”
Firmware Stage (1) • Two primary jobs in this stage: 1) Power-On Self Test (POST) – ensures system hardware (CPU, RAM, peripherals, etc.) is functioning properly 2) Load Master Boot Record (MBR) – contains drive partition table and loads first stage bootloader whose purpose is to load the second stage booloader (next stage)
Bootloader Stage (2)
• Loads the Linux kernel program into memory • Most common bootloaders - LILO - Linux Loader *Supports systems with BIOS *ELILO – Efi Linux Loader supports systems with UEFI - GRUB - Grand Unified Bootloader *Supports systems with UEFI
Bootloader Stage (2)
• Other bootloaders - SILO – SPARC Improved bootLoader *Supports Linux on Sun SPARC hardware -YABOOT – Yet Another Bootloader - Supports PowerPC hardware • Network booting - PXE– Preboot Execution Environment *For hardware that supports TFTP used to download the bootloader from a server