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The GRUB Boot Loader

When a computer running 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.

E.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:

Table E.1. Boot Loaders by Architecture

Architecture	Boot Loaders
AMD® AMD64	GRUB
IBM® eServer™ System i™	OS/400®
IBM® eServer™ System p™	YABOOT
IBM® System z®	z/IPL
IBM® System z®	z/IPL
x86	GRUB

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

Important — Supported file systems

The GRUB bootloader in Red Hat Enterprise Linux 6 supports only the ext2, ext3, and ext4 (recommended) file systems. You cannot use any other file system for /boot, such as Btrfs, XFS, or VFAT.