Hack 1. Give Your Computer the Boot
The beginning of all Linux journeys originates with the humble bootloaderthe small bit of code that jump-starts the whole boot process. Knowing how to configure your bootloader is almost requisite for using a Linux system. You also need to understand the bootloader if you want to configure your system to boot more than one operating system.
Within the exciting bootloader world are a number of choices for starting your computer. For x86 machines, there are two main contenders: LILO and GRUB. If you are running Linux on a Mac, LILO and GRUB are not available, and the main bootloader is called yaboot. Another potential situation in which you might need to boot a computer is when you are trying to boot a CD to install an operating system. Sometimes you can encounter a problem booting from a CD if your computer's BIOS does not support booting from CD-ROM or if your CD-ROM drive does not support booting from a CDR. You can resolve this problem with a tool called the Smart Boot Manager.
This hack explores the GRUB, yaboot, and Smart Boot Manager bootloaders.
1.2.1. Configure GRUB
Without a doubt, GRUB is a far more flexible boot manager than LILO. It enables you to add new kernels or boot parameters without having to install each update to the Master Boot Record (MBR). GRUB also allows you to pass parameters to it or to the kernel at boot time. Many Linux distributions now ship with GRUB as the default bootloader. Although GRUB is reliable and flexible enough to recover from most disasters, it is still advisable to back up your boot sector just in case something goes wrong. To do this, run the following command:
root@bar:~# dd if=/dev/hda of=/root/hda.mbr bs=512 count=1
GRUB is managed by a central configuration file which is either /boot/grub/menu.lst on Debian and Gentoo systems, or /etc/grub/grub.conf on Red Hat-based systems. This file contains a number of entries that indicate the name of the kernel, the root partition where the kernel can be found, and an initrd if one applies. Here is an example of a typical Linux kernel stanza in the GRUB configuration file:
title Ubuntu, kernel 126.96.36.199-2-386 root (hd0,0) kernel /vmlinuz-188.8.131.52-2-386 root=/dev/hda3 ro quiet splash initrd /initrd.img-184.108.40.206-2-386 savedefault boot
It's important to note how GRUB deals with disks and partition numbers. Unlike Linux, GRUB refers to the first disk as hd0 and the first partition as partition 0. In Linux this is designated as /dev/hda1. Basically, if the letters that designate the hard drive in Linux were numbers, you would subtract 1 from them. Therefore, an a (1) becomes 0, a b (2) becomes 1, and so on. Also, you would subtract 1 from the partition number itself. For example, a boot partition located on /dev/hdb3 becomes hd1,2 in GRUB parlance. In the previous stanza, you refer to the location of the kernel (root) as hd0,0, but on the kernel line, you refer to the root partition as /dev/hda3. Because it is a kernel parameter, it uses the normal Linux method of referring to disks and partitions. The final part of the stanza uses savedefault to make the stanza a default option in the GRUB menu, and the command boot actually boots the system.
If you want to add another operating system, simply add it elsewhere in the configuration file. A Windows stanza looks like this:
title Windows 95/98/NT/2000 root (hd0,0) makeactive chainloader +1
When you are booting non-Linux operating systems (most likely Windows), you usually will need to use the makeactive and chainloader keywords. The makeactive keyword is used to set this partition as GRUB's main root filesystem device. The chainloader command is used so that the bootloader can call another bootloader (usually the Windows boot manager) instead of loading a Linux kernel.
If your boot manager is hidden, it is probably because your distribution set it to be hidden. Look for the parameter hiddenmenu in your grub.conf file, and comment it out if you want to see your boot menu. You might also have a default option, which specifies the stanza in the file you want to be your default boot configuration. As an example, if you want the first stanza to be the default, use this:
1.2.2. Configure the Mac Bootloader
Mac versions of Linux use a different bootloader called yaboot. Although not quite as flexible as GRUB, yaboot takes a similar stanza-based approach to specifying kernels. Here is a typical Linux kernel on the first partition (you should adjust the path on the image line when your kernel is located elsewhere):
image=/vmlinux-220.127.116.11 label=NewLinux read-only append="quiet splash" initrd=/initrd.img-18.104.22.168
To enable your system to boot Mac OS X as well, simply add the following option to /etc/yaboot.conf and indicate the correct partition that contains Mac OS X (you can determine the right partition by running a partitioning tool such as cfdisk):
When you have edited the file, you need to run the ybin program to write the boot sector. If you use the -v option, you can see the output of the command:
root@bar:~# ybin -v
1.2.3. Boot from a CD-ROM
The vast majority of Linux distributions are available on CD. Their installation program loads automatically when you boot the computer with the CD in the drive. On newer machines, this process is not a problem (though you might need to enter your BIOS setup program and select the CD drive as the first bootable device). On older computers, this can be an issue because some computers do not support a bootable CD drive. Another common complaint with old secondhand computers is that the BIOS might be password-protected but no one knows the password. This means you can't make the CD drive the first boot device.
Many Linux distributions get around this problem by including a floppy-disk boot image that you can use to create boot floppies. These floppies "jump-start" the installation process and give access to the CD despite any hardware shortcomings. The CDs usually include a tool called rawrite that can be used to copy the boot images to the floppies. If this works with your distribution, the problem is solved, but unfortunately not all distributions include a floppy boot image.
Another solution is to use a tool called the Smart Boot Manager (http://btmgr.sourceforge.net). This useful little utility creates a boot sector on a floppy disk that allows you to boot from the CD and use the CD installation program. To use the Smart Boot Manager, you need to download it from http://btmgr.sourceforge.net/download.html and unpack it to your disk. I recommend downloading the latest version that is statically linked. The software includes a program you can use to install the Smart Boot Manager to the floppy disk in /dev/fd0:
foo@bar:~$ sbminst -t us -d /dev/fd0
This command installs the English theme into the boot sector on device /dev/fd0. A number of different languages are supported across the different themes. These include:
When you boot into the Smart Boot Manager, you can configure the software from within the program with a simple-to-use text-based windowing interface.