CLTB :: Setting GRUB.

The GRand Unified Bootloader (GRUB) has all LILO features and more, unlike LILO, GRUB is not specific for Linux it could deal with many other Unix systems and thats where the name come from. GRUB configuration file is '/boot/grub/grub.conf' or '/boot/grub/menu.lst' (make a symbolic link if you are not sure), the most important GRUP feature is that it could mount and access to files (on ext2,ext3,reiserfs,xfs,jfs,FAT and many more file system types) so you don't need to run it each time you edit the file or install a kernel, it could boot systems or pass options that it's not configured to boot with an interactive BASH like prompt, it has an on line help, GRUB could be used when there is a change with your disk 'master' and 'slave' flags. When GRUB starts it display a text or graphical a pre-configured menu of system to boot with a timer, use arrows then press ENTER to boot, you could press 'e' (if allowed) on any item to edit it before booting, press 'c' (if allowed, I won't say it again) to enter GRUB interactive prompt, if there is lock on edit,command line or some items on the window, to open the lock, press 'p' then type the GRUB password.

If GRUB fails to locate its configuration file, then GRUB will show a BASH like prompt, press 'TAB' once or twice for auto-complete, type 'help' followed by any command to get help about it. GRUB device names is unified in all Unix systems, its NOT the same as Linux nor any other Unix, devices are written between parenthesis '()', the hard disk is 'hd' adn floppy is 'fd' followed by a number starting from 0, if you want a specific partition add its number (counting from 0) after comma ',', for example '/dev/hda1' is '(hd0,0)' and '/dev/hda5' will be '(hd0,4)', the whole floppy is '/dev/fd0' is '(fd0)'.

4.5.2. Using GRUB.

There are two types of booting methods, first is used to boot with mono-boot or unsupported operating systems like DOS,Windows, it just load another boot loader (on the first sector of that partition of that OS) and it's upto it to boot that system, using 'chainloader' command for example 'chainloader (hd0,0)+1' to load the first sector on the first partition of the first hard disk, the number after '+' is the number of sectors (to load from the current position, 0 sector), another example 'chainloader (fd0)+1' to boot the floppy (there is no partitions on the floppy), well, after this it does not boot! it just collect information and after all issue 'boot' command to do the booting. The 'chainloader' could boot not only boot sectors but also files, you could save the boot sector on a file like 'bootsect.dos' on the first partition, to boot use something like
'chainloader (hd0,0)/bootsect.dos' then 'boot', this way GRUB could load LILO or another GRUB somewhere else. Next method is for multiboot systems like Linux and other Unix systems, we use 'kernel' command followed by kernel file location followed by arguments, for example a kernel located on the first logical partition on '/dev/hda5' in GRUB terminology it's '(hd0,4)' and the file name is '/boot/vmlinuz' the command is 'kernel (hd0,4)/boot/vmlinuz', You could pass argument to kernel after kernel file location, for example 'kernel (hd0,4)/boot/vmlinuz root=/dev/hda5 ro', then (after kernel) if it need a initial RAM disk use 'initrd' followed by it's compressed RAM disk image file, for example 'initrd (hd0,4)/boot/initrd.gz', now type 'boot'.

To save some typing, you could omit device, just specify a default device with 'root' followed by the device to mount, for example:

root (hd0,4)
kernel /boot/vmlinuz root=/dev/hda5 ro
initrd /boot/initrd.gz
boot

rootnoverify (hd0,0)
chainloader +1
boot

rootnoverify (hd0,0)
makeactive
chainloader +1
boot

4.5.3. GRUB configuration file.

# menu.1st: Sample boot menu configuration file for grub
# 	by Moayyad al-Sadi <alsadi[at]gmail.com>
# default item is number 0 item (1st one)
default=0
# if can't then try the 2nd one
fallback 1
# boot if nothing selected in 7sec
timeout=7
# do not allow grub console and editing
# unless password is given
password --md5 $1$ab0cdf.152467795
# for grapical mode
# a 640x480x16 compressed xpm image
	splashimage=(hd0,4)/boot/grub/logo.xpm.gz
	background 000080
	foreground ffffff
	shade 1
# set color to blue not needed in graphics
# color white/blue blink-yellow/magenta
title Linux 
	root (hd0,4)
	kernel (hd0,4)/boot/vmlinuz ro root=/dev/hda5 hdd=ide-scsi
# you can give long titles
title Linux in text mode
	root (hd0,4)
	kernel (hd0,4)/boot/vmlinuz 2 ro root=/dev/hda5 hdd=ide-scsi
title Windowz (Bug mode)
	# don't boot without password
	lock
	rootnoverify (hd0,0)
	chainloader +1
	makeactive
title floppy
	# don't boot without password
	lock
	chainloader (fd0)+1
title Change console colors
	color light-green/brown blink-red/blue

The wallpaper is specified witth 'splashimage', which is a 16 color (4 bits) and '640x480' gzipped XPM file, I think that it differs from distribution to another, I tried GRUB 0.92 shipped with RedHat 8.0 and it's by default use graphical menu with splash image, the same version shipped with Mandrake 9.0 but splash image is not configured by defualt and it will be ignored if you add it, GRUB shipped with Debian is not configured by defualt to show a splash image but you may create one and it will work.

To install grub for the first time, type 'grub' to get GRUB prompt then type: (only bold)

4.5. Setting GRUB.

Section contents:

4.5.1. Introduction.

4.5.2. Using GRUB.

4.5.3. GRUB configuration file.

4.5.4. GRUB rescue boot floppy.