Linux Boot Loader

In our last post we have seen basics of Linux System Initialization. Now lets take a depth look of Linux Boot Loader.

There are two possible ways to configure boot loaders:

1. Primary Boot Loader: Install the first stage of boot loader in to the MBR but the boot loader must be configured to pass control to any other desired OS.
2. Secondary Boot Loader: Install the first stage of boot loader in to the boot sector of any of partition on disk. But other boot loader must be installed and configured in MBR to pass control to OS.

There are two basic boot loaders used in Linux Distributions.

1. GRUB - Grand Unified Boot Loader
2. LILO - Linux Loader (Obsoleted)

In this article we talk about GRUB only.

Working of GRUB:

• To select an Operating System from the HDD.
• Identify the partition with the help of appropriate boot files.
• Locate kernel on the HDD.
• Run initial ram disk to set up the kernel and associated modules.

Benefits of GRUB:

• Provides Password based security at system start up.
• Easy to edit during boot process without making persistent changes.
• Allows booting from WindowsXP/Vista/7 from the MBR.
• Supports LBA (Logical Block Addressing) mode, which can help system to find the boot files if thay are beyond the 1024th cylinder on HDD.

GRUB Configuration:

Configuration of GRUB is very simple but it's vary according to the different Linux distributions.