GRUB boot manager

The GRand Unified Bootloader (GRUB) replaces the LInux LOader (LILO) as the default boot manager for Red Hat Linux 7.2. When your computer starts up, the first thing it does is run the boot manager. The boot manager lets you select which operating system to boot (if you have more than one on your computer), and then hands control of the rest of the boot process to the operating system you chose.
GRUB can boot both multiboot and non−multiboot operating systems. Multiboot operating systems let you pass arguments to the operating system when you boot. Non−multiboot systems simply allow you to use a feature called chain−loading, which allows it to simply load another boot loader to start the operating system.
For multiboot systems, GRUB allows you to pass options to the kernel at boot time. For example, you can identify a hardware device to use a particular driver or override auto−detection of a device. You can also use a configuration file to name and identify the locations of boot images on your computer.