The Menu Configuration File

The configuration file, which is used to create the list in GRUB's menu interface of operating systems to boot, essentially allows the user to select a pre-set group of commands to execute. The commands given in the Section called Commands can used, as well as some special commands that may only be used in the configuration file.

Special Configuration File Commands

The following commands can only be used in the GRUB menu configuration file:

color <normal-color> <selected-color> — Allows for the set up specific colors to be used in the menu, where two colors are configured as the foreground and background. Use simple color names, such as red/black. For example:
color red/black green/blue
default <title-name> — The default entry title name that will be loaded if the menu interface times out.
fallback <title-name> — If used, the entry title name to try if first attempt fails.
hiddenmenu — If used, prevents the GRUB menu interface from being displayed, loading the default entry when the timeout period expires. The user can see the standard GRUB menu by pressing the [Esc] key.
password <password> — If used, prevents the user who does not know the password from editing the entries for this menu option.
Optionally, it is possible to specify an alternate menu configuration file after the <password>, so that, if the password is known, GRUB will restart the second stage of the boot loader and use this alternate configuration file to build the menu. If this alternate file is left out of the command, then a user who knows the password would be able to edit the current configuration file.
timeout — If used, sets the interval, in seconds, before GRUB loads the entry designated by the default command.
splashimage — Specifies the location of the splash screen image to be used when GRUB boots.
title — Sets a title to be used with a particular group of commands used to load an operating system.

The # character can be used to place comments in the menu configuration file.

Configuration File Structure

The commands to set the global preferences for the GRUB menu interface are placed at the top of the file, followed by the different entries for each of the operating systems to boot.

A very basic GRUB menu configuration file designed to boot either Red Hat Linux or Microsoft Windows 2000 might look as follows:

default=linux
timeout=10
color=green/black light-gray/blue

# section to load linux
title linux
root (hd0,1)
kernel /vmlinuz root=/dev/hda5
boot

# section to load Windows 2000
title windows
rootnoverify (hd0,0)
chainloader +1

This file would tell GRUB to build a menu with Red Hat Linux as the default operating system, set to autoboot it after 10 seconds. Two sections are given, one for each operating system entry, with commands specific to this system's disk partition table.

Actually configuring a GRUB menu configuration file to boot multiple operating systems is beyond the scope of this chapter. Please consult the Section called Additional Resources for detailed information about booting various operating systems with GRUB.