GRUB -- GRand Unified Bootloader

version 0.5

by Erich Boleyn

Master Contents

Some of these contents are included in other pages.

NOTE: Up-to-date versions of this documentation directory can be found at The specifics might be for a newer version of the program, so check the online NEWS file for details about the differences.


GRUB is an attempt to produce a bootloader for IBM PC-compatible machines that has both the capability to be friendly to beginning or otherwise non-technically interested users and the flexibility to help experts in diverse environments. It is currently most useful for users of at least one of the various free UNIX-like operating systems, though it can be used with most any PC operating system.

This project actually started because we wanted to boot the GNU HURD operating system on top of Mach4 on an IBM PC-compatible system in a manner compliant with the Multiboot Standard, which was put together as a general solution to the problem of the different boot formats and the functionality they need. I then tried to add support for the extra functionality to the standard bootloader used for FreeBSD. The number of things I had to do to get it all to work multiplied until it was obviously necessary to start from scratch with something different.

GRUB has evolved a long way from it's beginnings as a multi-module bootloader. Several of the techniques used have no analogue in the rest of the free software world, and a few are apparently superior to most proprietary OSes as well. The documentation here and in the multiboot proposal should be very useful to prospective OS and bootloader writers for PCs.

The name comes from the acronym, but also from the realization that although a grub is one of the smaller (and less interesting) critters - barely worthy of notice - it is nearly ubiquitous and vital to the order of things.

Thanks To

Distribution and Status

GRUB is currently available under the GNU General Public License. This should not be an issue for OS developers or users who dislike the terms of the GPL, as it is a separate package, and will not have any licensing impact upon their own work or installation. If it is still an issue, send me e-mail and maybe we can work something out.

The publically available releases are available on my FTP site, and I believe they will get included in the GNU FTP sites as well.

Here are links to the NEWS file, TODO list, and list of known BUGS.