Chapter 2. The GRUB Boot Loader

Chapter 2. The GRUB Boot Loader

2.1. Boot Loaders and System Architecture
2.2. GRUB
2.2.1. GRUB and the x86 Boot Process
2.2.2. Features of GRUB
2.3. Installing GRUB
2.4. GRUB Terminology
2.4.1. Device Names
2.4.2. File Names and Blocklists
2.4.3. The Root File System and GRUB
2.5. GRUB Interfaces
2.5.1. Interfaces Load Order
2.6. GRUB Commands
2.7. GRUB Menu Configuration File
2.7.1. Configuration File Structure
2.7.2. Configuration File Directives
2.8. Changing Runlevels at Boot Time
2.9. Additional Resources
2.9.1. Installed Documentation
2.9.2. Useful Websites
2.9.3. Related Books

When a computer with Red Hat Enterprise Linux is turned on, the operating system is loaded into memory by a special program called a boot loader. A boot loader usually exists on the system's primary hard drive (or other media device) and has the sole responsibility of loading the Linux kernel with its required files or (in some cases) other operating systems into memory.

2.1. Boot Loaders and System Architecture

Each architecture capable of running Red Hat Enterprise Linux uses a different boot loader. The following table lists the boot loaders available for each architecture:

Architecture Boot Loaders
AMD® AMD64 GRUB
IBM®eServer™ iSeries™ OS/400®
IBM®eServer™ pSeries™ YABOOT
IBM® S/390® z/IPL
IBM®eServer™ zSeries® z/IPL
Intel® Itanium™ ELILO
x86 GRUB
Table 2.1. Boot Loaders by Architecture

This chapter discusses commands and configuration options for the GRUB boot loader included with Red Hat Enterprise Linux for the x86 architecture.