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List:       opensuse
Subject:    [opensuse]  Re: Grub bugs ... should I file separate bugs for each    one?
From:       Joachim Schrod <jschrod () acm ! org>
Date:       2009-06-13 15:27:07
Message-ID: h10ggb$bb6$1 () ger ! gmane ! org
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Greg Freemyer wrote:
> I'm confused by this whole thread.
> 
> Is this a reasonable summary:

No.

> Form latest to earliest use of labels during boot:
> 
> /etc/fstab   -  by_label, etc., fully supported
> 
> /boot/grub/device.map - by_label, etc., fully supported

This is not used at boot time, see below.

> /boot/grub/menu.lst - by_label, etc., fully supported
> 
> MBR used to invoke grub stage 1.5 or 2.  -  No label support, so the
> user can be screwed every time a user adds / removes disks?

Yes, Grub at boot time is independent from Linux and doesn't know
about labels. But that's what /boot/grub/device.map is for: To use
Linux' labels (actually, device files with label names) to install
Grub to MBR.

When a user adds or removes a boot disk, or changes partitions on
his boot disk that are involved in booting or are before the boot
partition, he or she must re-install grub. That means: Not
re-installing the grub rpm, but calling the command grub-install
with apropriate parameters.

grub-install then uses the information from /boot/grub/device.map
to write to the MBR where the stage 1.5 loader can be found at run
time. This *is* the disk label support for Grub -- or for what else
do you think that /boot/grub/device.map is used?!

Look:

 -- If you're using Grub, you have to call grub-install at every
    disk change that involves boot partitions, maybe after updating
    /boot/grub/device.map. (Maybe Yast2 does the latter for you,
    dunno.)

 -- If you're using LILO, you have to call LILO at every disk
    change *and* at every kernel installation.

I.e., one has to initialize the MBR with all boot management
facilities. With Grub, one actually has to initialize it less often
as with LILO. But this does not mean that one has to reinit it
never again. Does that make concept clearer?

Btw, if all else fails, there is still the documentation, i.e.,
info grub. ;-)

	Joachim

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Joachim Schrod				Email: jschrod@acm.org
Roedermark, Germany

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