If you discover that a certain application no longer works for you, you can go back to a previous kernel to try to run your program. GRUB, the boot loader found in most Linux distributions, lets you choose among operating systems and kernels installed on your box. Many people, however, fear that messing with GRUB may ruin their system, because of its many esoteric options, and configuration file text that often contains no help comments. QGRUBEditor can help you view and edit the GRUB boot loader from a graphical user interface.

If you're still lumbering along with the antique Linux Loader LILO, you really ought to consider migrating to GRUB, the Grand Unified Bootloader. LILO is quite good, and, as the saying goes, if it ain't broke .... But GRUB has some advantages that make it, in my opinion, the Bootloader of today's generation. Here's why...

Grub is a world-class boot loader with insufficient documentation. In many ways it blows the doors of LILO. For instance, it's MUCH easier to use Knoppix to rebuild a grub boot loader than to rebuild a LILO boot loader. However, until you're comfortable with grub, it might seem just the opposite. All too often grub dumps you at a grub> prompt with no hint of what you should do. You might have heard that a successful reboot is just three commands away, but which commands? The state of grub's documentation is such that you can't figure it out unless you already know grub.

The reason anyone would use the GRUB menu is to dual-boot two different operating systems. All it is is a simple DOS menu that you select which operating system you want to load during boot-up.

LILO (Linux Loader) and GRUB (GRand Unified Bootloader) are both configured as a primary boot loader (installed on the MBR) or secondary boot loader (installed onto a bootable partition). Both work with supporting operating systems such as Linux, FreeBSD, Net BSD, and OpenBSD. They can work with unsupported operating system, such as Microsoft Windows XP, in the configuration file. Both allow users—root users—to boot into single-user-mode.

GRUB is not dependent upon any operating system. It was written to conform with the Free Software Foundation's Multiboot Specification, which allows it to boot almost any operating system. In fact, it can boot multiple operating systems on computers that have more than one installed on their hard drives. Among GRUB's features:

GRUB gobbles up LILO any day of the week. It is faster to load, more resiliant to configuration errors, and more secure when you try to lock down the config using boot password. However, it does have two missing features:

1. LILO -R

on Lilo, this changes the default for the next reboot only.

Super Grub Disk (SGD) is a specialty rescue CD for emergency repairs on boot sectors. Despite its name, SGD not only manipulates the Grand Unified Bootloader (GRUB), but also works with the content of other master boot records as well. Available in English, French, and Castillian Spanish, SGD also works with a variety of operating systems and supports all the basic options needed to manipulate how a hard drive boots.

GRUB is a boot loader, which means it passes control of the boot process from the Power-On Self Test (POST) to the kernel of your GNU/Linux distribution. GRUB works in a modular, layered fashion so that any unneeded modules are not loaded. Not only does this reduce execution time, but it saves valuable resources when running from removable media. GRUB optionally loads its configuration file at run/boot time, so you don’t have to type in commands manually each time. However, the command-line option is still available in case there is an error in your configuration file.

The GRUB boot loader is the default boot loader installed by Red Hat Enterprise Linux (and other distributions such as SUSE Linux Enterprise Server, Mandriva, Fedora Core and Gentoo, amongst others).