On Sun, 26 Oct 2008 13:25:44 -0700, Darren New wrote:

> Jim Henderson wrote:
>>>> Thing is, it shouldn't require a change to the active partition list.
>>> It doesn't *require* it. It *allows* it.
>> 
>> No, I mean in order to boot a different partition.
> 
> Windows and GRUB are the same in this respect. If the active partition
> is, for some reason, unreadable, you won't get a menu to boot the other
> partition. However, you can use a non-OS tool (fdisk off a dos disk,
> say) to change the active partition and boot the other OS.
> 
> It's a two-stage boot. You're talking about the second stage. I'm
> talking about the first stage.

Oh, right - yes, and both platforms use the two-stage system these days.

>> Probably, yes - though it's probably easier to modify the Grub setup at
>> that point and just add the Windows install.  Most people I know who
>> install Windows second, though, use a VM rather than a native boot.
> 
> There are definitely more options now than there were, yes. :-)

Absolutely. :-)

>> It means that GRUB on my system here is using the active partition.  I
>> don't know what's in the MBR on this laptop's hard drive, but the
>> settings when I go into YaST and look indicate that it's installed to
>> the first sector of the active partition.
> 
> It's most likely installed to both. It's a two-stage boot. Maybe that's
> what's confusing the conversation.

Perhaps.

> The first stage is to load the MBR off (basically) sector zero of the
> hard drive, which happens to include the partition table. The *stnadard*
> MBR then looks at the partition table, finds the active partition, moves
> itself out of the way, reads the first sector of the active partition
> into the same place it was, and jumps to it.
>
> Only after that second step do you get any kind of menu. If you delete
> NTLDR or /boot off the active partition, you're not going to have an
> opportunity to boot off a different partition. With the standard MBR,
> you don't have to put NTLDR or /boot back, you just have to change the
> active flag.  Last I experiemented, the GRUB MBR booted the GRUB
> partition even if it wasn't marked active, which means if your GRUB
> partition is corrupt, you're SOL.

Well, only as far as that disk is - a bootable rescue disk can fix that, 
but also in my experience GRUB can get to a point where you can type in 
commands to boot the system.  I used to have to do that with RH9 systems 
I'd imaged on occasion.  So even if it didn't read the menu, I could get 
the system up to a point where I could fix the menu.

Jim

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