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2. LILO principles

Without getting too deep, let's just explain what booting a PC is all about.

2.1 The First Inhabitant: The BIOS

When a PC starts, the first program to take control is the BIOS, which is resident in ROM. After initializing most hardware in your machine, it attempts to load a tiny program, normally either from the first sector of the floppy or the first sector of the first hard drive. This program is called the Master Boot Record or MBR for short.

2.2 From the MBR of the hard drive to the OS

The MBR of the hard drive, using the BIOS, does one of two things.

The first possibility (like the MBR included with DOS) is that it locates the active partition and loads the first sector of that partition. This sector contain a tiny little program which knows a little bit more about the internals of the OS living in that partition. It will proceed to load either basic components of the system or simply a more sophisticated boot loader which will finish the job.

Alternatively, the MBR of the hard drive can load information directly from one of the partitions, and use that to load OS's on any partition. LILO can be configured this way; the OS/2 boot loader and Partition Magic, two other well-known bootloaders, do the same.

2.3 The floppy's boot sector

The boot sector of a floppy may be compared to the boot sector of the active partition. It normally proceeds to load the OS living on the floppy.

2.4 And LILO

LILO is fairly flexible, here is why.

2.5 LILO, Linux, and the world

When installing Linux on a system with several OS's (besides Linux), take this as a rule of thumb: Install and configure booting for all the other OS's first, because they are less flexible. It will then be easier to set up LILO to boot all the other OS's


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