1. Linux Boot Loaders

2. ♦ Overview A boot loader is a small program that exists in the system and loads the operating system into the system’s memory at system boot. This module deals with two most popular boot loaders of Linux, LILO and GRUB. ♦ Lessons Covered in this module ► Lilo Loader ► Grand Unified Boot Loader Module 7 – Linux Boot Loaders

3. Linux Boot Loaders Lesson 1 – Lilo Loader ♦ Introduction LILO or Linux Loader is a boot loader for Linux. A boot loader is a small program that exists in the system and loads the operating system into the system’s memory when the system boots. Boot loader also starts the operating system. ♦ Topics Covered in this lesson ► LILO, the Boot Loader ► Configuring LILO

4. Linux Boot Loaders ♦ LILO is a flexible boot loader for Linux, which is independent of a file system. ♦ LILO loads itself into the computer’s memory in two stages ► Stage1 – This stage, also known as primary boot loader is read into memory by the BIOS from the master boot record ► Stage 2 - This stage, also known as secondary boot loader is read into memory and it displays the Red Hat Linux initial screen Topic 1 – LILO, the Boot Loader

5. Linux Boot Loaders Topic 2 – Configuring LILO ♦ To install LILO, it is necessary to know the location of /boot partition. ♦ It is also necessary to know the location of other installed operating systems ♦ LILO can be installed for the first time using a shell script named QuickInst ♦ LILO can be uninstalled using the lilo –u command

6. Linux Boot Loaders ♦ Introduction Grand Unified Boot loader or GRUB is a boot loader which operates like LILO and it is presently the default boot loader. GRUB sets the user to select the operating system or kernel to be loaded when a system boots up. It also permits the users to pass arguments. ♦ Topics covered in this lesson ► GRUB, Grand Unified Boot Loader ► GRUB Installation and Configuration ► GRUB and the Boot Process Lesson 2 – Grand Unified Boot Loader

7. Linux Boot Loaders ♦ GRUB an acronym for Grand Unified Boot loader, is a program or boot loader. ♦ It lets the user to pass arguments to the kernel GRUB will install a boot loader to the MBR ♦ GRUB will permit to set particular instructions in the MBR. ♦ These instructions also include passing special instructions to kernel when they boot or find system parameters before system boot. Topic 1 – GRUB, Grand Unified Boot Loader

8. Linux Boot Loaders ♦ GRUB has the provision of a true command-based, pre-OS environment on x86 machines. ♦ This will help the user in being more flexible in loading operating systems with denoted options or collecting information about the system ♦ GRUB will support Logical Block Addressing (LBA) mode ♦ ext2 partitions can be read by GRUB. Some of the important features of GRUB

9. Linux Boot Loaders Topic 2 – GRUB Installation and Configuration ♦ GRUB can be installed during installation and also post installation.. ♦ GRUB Configuration ♦ When Grub is installed two configuration files are created and they are ► /boot/grub/grub.conf is the configuration file of GRUB. ► /etc/grub.conf is a link file to /boot/grub/grub.conf and the user can make the configuration changes here Contd …

10. Linux Boot Loaders Sample copy of Grub.conf file

11. Linux Boot Loaders Topic 3 - GRUB and the Boot Process ♦ Grub gets loaded into the memory of the system in the following stages: ► The Stage 1 or primary boot loader is read into memory by the BIOS from the master boot recorder (MBR). ► The Stage 1.5 boot loader is read into memory by the Stage 1 boot loader if required. ► The Stage 2 or secondary boot loader is read into memory. ► The secondary boot loader will read the operating system or kernel and the contents of /boot/sysroot/ into memory

12. Linux Boot Loaders ♦ Summary ► LILO, the Linux loader is the boot loader for Linux which boots the operating system whenever the system boots ► The configuration file of LILO is maintained in /etc/lilo.conf file ► GRUB, an acronym for Grand Unified Boot loader is the most commonly used boot loader for Linux ► Red Hat Linux has /boot/grub/grub.conf as the configuration file. ♦ Question and Answer Session Conclusion