[SWLUG] Mulicard Reader in MDK 9.0

[Robert McQueen]

On Fri, May 02, 2003 at 09:12:51AM +0100, Mark Fisher wrote:
> Yep, very true.  I couldnt find the exact reason in google within the minute 
> so ill try to explain from memory.  In basic lilo doesnt actually read 
> lilo.conf during bootup, only when it is run from the command line.  During 
> bootup it reads some sort of cached config that is stored in the boot sector 
> [If I remember correctly].  Whereas the modern 'replacement', grub, does 
> actually read grub.conf :o)
> 
> - -- 
> Regards,
> 
> Mark Fisher

The specific reason is that when you run '/sbin/lilo', it reads
lilo.conf and queries the kernel to find where on disk the kernel images
are. It embeds this blocklist, and your options, and the location of
your menu/whatever in /boot, and puts this all in the boot sector with
the bootloader code itself.

Grub has a 'stage1' which is roughly equivalent to the lilo bootloader.
When you install Grub, the blocklist that is put in is the location on
your /boot partition of a 'stage1.5', of which there are many, which
let Grub read the filesystem. Grub can then read the filesystem to load
in 'stage2', which is the cool interactive shell/menu/etc, and has the
ability to load your menu.lst file, follow symlinks, load other 'stage1.5's
and hence read most common filesystems, tab complete filenames (it even
has a 'cat' equivalent) and other niceties.

On a Debian system, the kernel image packages maintain symlinks for
/vmlinuz (the last installed kernel) and /vmlinuz.old (the previous
kernel). My Grub menu.lst hence never changes, I have two menu entries
for the current kernel, multi and single user mode, and two entries for
the previous, in multi or single user mode, and Grub follows the symlinks
to whatever kernel image is currently installed. If they break (not that
that's ever happened), I can tab complete the name of a kernel in /boot,
or even load memtest86 manually like this.

A Grub boot floppy has 'stage1' followed by 'stage2' and lets you load
any kernel image off any filesystem, and even read configuration files
or whatever, so constitutes the ideal swiss-army bootdisk. And yes, Grub
also lets you chain load "other OSes". It really is very cool.

Regards,
Rob