GRand Unified Bootloader

From OptionC

Grub stub

GRUB (or GNU GRUB) is the GRand Unified Bootloader.

The Grub Manual (http://www.gnu.org/software/grub/manual/html_node/) gives most of the information you need in order to install and use GRUB. This page will focus on using GRUB with Xen.

A sample entry for booting Xen is:

title     Debian + Xen 2.0.6 / Linux 2.6.11 (Stable)
root      (hd1,1)
kernel    /boot/xen.gz dom0_mem=262144 noreboot
module    /boot/vmlinuz-2.6.11-xen0 root=/dev/hdd2 ro console=tty0

In brief, this tells GRUB to boot Debian with Xen 2.0.6 from /dev/hdd2, the second partition on the /dev/hdd drive. It says the kernel is to be found in /boot/xen.gz (Xen) with the real Dom0 Linux kernel at /boot/vmlinuz-2.6.11-xen0. The root device is to be /dev/hdd2.

The dom0_mem option allows the administrator to set the initial memory for dom0. In this case 256 MB (or 262,144 KB). Version 2.x of Xen requires this option to be set in Kilobytes. Future versions (3.x and beyond) are expected to use suffixes ("B", "K", "M", and "G", representing "Bytes", "Kilobytes", "Megabytes" and "Gigabytes", respectively) to allow for simpler definition of memory limits.

Additional options can be found in the Xen User Manual under Boot Options (http://www.cl.cam.ac.uk/Research/SRG/netos/xen/readmes/user/user.html#SECTION03320000000000000000).

Some of the important ones are:

* noreboot       - if an error occurs while booting, don't automatically reboot. This allows those of us who are slower readers the necessary time to read errors on the screen.
* console={list} - define location(s) for the Xen console I/O.
* mem=###        - define the limits of physical RAM.

Recommended Reading

• Grub Manual (http://www.gnu.org/software/grub/manual/html_node/)
• Grub From the Ground Up (http://www.troubleshooters.com/linux/grub/grub.htm)
• Xen Boot Options (http://www.cl.cam.ac.uk/Research/SRG/netos/xen/readmes/user/user.html#SECTION03320000000000000000)