How to setup boot loaders

This page (hopefully) will explain everything you should know about the major bootloaders so that you can configure them to your liking.

LILO, GRUB and NT Boot Loader

Comparison Table

	LILO	GRUB	NT Boot Loader
boot selector	line input text menu graphical menu	line input text menu	text menu
OS support	GNU/Linux	FreeBSD, NetBSD, OpenBSD, GNU/Linux	none
Windows Support	via chain-loading	via chain-loading	WinNT, Win2K, WinXP
supported filesystems	block offset based	BSD FFS, FAT16, FAT32, Minix fs, ext2fs, ReiserFS, JFS, XFS, VSTa	FAT16, FAT32, NTFS
Partition designation example (second partion on first harddisk)	/dev/hda2	(hd0,1)	multi(0)disk(0)rdisk(0)partition(2)

GRUB

GNU GRUB is surely the most powerful of the bootloaders listed here. Besides featuring a nice and comfortable boot menu and a human readable easy to understand configuration file, it offers an interactive console which can be the perfect tool for recovering boot problems.

Creating a GRUB bootdisk

As a fallback it is always good to create a GRUB bootdisk, especially because for GRUB this is very quick and simple.

• Insert a formatted floppy disk to your floppy drive, but do not mount it.
• Execute the following commands to create the boot disk (you may need to change /usr/share to /usr/lib):

# dd if=/usr/share/grub/i386-pc/stage1 of=/dev/fd0 bs=512 count=1

# dd if=/usr/share/grub/i386-pc/stage2 of=/dev/fd0 bs=512 seek=1

That's it. The created disk will boot directly into the interactive GRUB console. Use help there to get a list of available commands.

Hint:

You can get partition and file listings within GRUBs console through TAB completion.

Installation of a GRUB boot sector

• Usually the files needed for GRUB should reside in /boot/grub.
• Copy over the necessary stage files from /usr/share/grub/i386-pc/ or /usr/lib/grub/i386-pc. You will need stage1, stage2 and usually one or more stage 1.5 files matching your filesystem. Usually these are e2fs_stage1_5, reiserfs_stage1_5 or iso9660_stage1_5. Look into the directory for support of other filesystems.
• To get the comfortable GRUB boot menu you will have to create the file /boot/grub/menu.lst. The format of it is explained in GRUBs info page ({{{2}}} info grub).
• Once everything is setup in /boot/grub, launch the GRUB console by running # grub.
• Within the console select the partition on which your /boot/grub directory resides using the root command, i.e. for the second partion on the first harddisk (/dev/hda2), enter

root (hd0,1)

• After that is successfully done, install the bootloader to the MBR using

setup (hd0)

• Reboot your machine to try if it works.

NT Boot Loader

The Windows 2000/XP boot loader is a bit hard to tweak if you want something else than use it to choose between your Windows installations.

The NT Boot Loader generally works like this:

• The booted partitions (i.e. the active one) boot sector looks for ntldr.exe on the active partitions filesystem. NTLDR is the actual boot loader and control is given to it if it's found. Else the boot process will fail.
• NTLDR looks for the boot.ini file on the active partition to read it's configuration. If more than one operating systems are configured in the file and the delay parameter is not 0, then the NT boot menu is displayed.
• When the user chooses a system, the delay time runs out or there is only one given system, NTLDR will start that system.

Using the NT Boot Loader to boot Linux

ToDo...

Using LILO or GRUB to boot Windows

When you want to configure a linux boot manager to boot Windows, there are some aspects to care about.

• First of all, do not install LILO or GRUB to the Windows partitions boot sector. This would overwrite the Windows boot loader and Windows would not be bootable anymore. In fact it is always a good idea to install the linux bootloader to the MBR.
• Take care that at least at the time of booting, your Windows partition is the active one. As long as the LILO/GRUB is installed to the MBR, the Linux boot process doesn't depend on the active partition flag. So in most cases you can just set it on the Windows partition (using i.e. # fdisk /dev/hda) and leave it. However, there are cases requiring a more dynamic handling. GRUBs makeactive command can help you here.

LILO configuration

Given that /dev/hda2 would be your Windows partition, a typical /etc/lilo.conf section for booting it with LILO would be:

other=/dev/hda2
label=win

GRUB configuration

Given that /dev/hda2 would be your Windows partition, a typical /boot/grub/menu.lst section for booting it with GRUB would be:

title Windows
rootnoverify (hd0,1)
makeactive
chainloader +1