update grub + 2 ubtuntu installs with shared /boot

[Philip Lawatsch]

Gary W. Swearingen wrote:
> Philip Lawatsch <philip at lawatsch.at> writes:
> 
>> I've no problem understanding / using grub, I've only got a problem
>> understanding all the automatisms which are in ubuntu and deal with grub.
> 
> Yeah.  I hear a new Slackware version has come out, or soon.

What would slackware have to do with that?

>> Well, if I want the comfort of automagically booting the correct kernel
>> even after an upgrade then I have to have some hack in place to allow
>> update-grub to update menu.lst without breaking the other install.
>>
>> For this to work with 2 installs every install needs to have a seperate
>> menu.lst
> 
> And thus two /boot dirs, which I thought you said you didn't want.

Yes, I do not want that, and thus would like to know how to avoid it
(while still getting new kernels automatically installed into my boot
system)

>> And for this to work I would need at least 2 grub installs, where one
>> grub starts the other grub (and have only one grub installed in the mbr).
>>
>> In my case I'm going to have one grub installed in the mbr which will
>> start a bsd install, a windows install and then a different grub for
>> each of the two ubuntu installs.
> 
> Sounds good, if the ubuntu install offers installing grub bootloader
> to a partition.  
> You didn't say where the MBR's menu.lst is, but let's
> say in the BSD "/boot/grub".  

I currently only have one menu.lst.

> You could then edit that to boot the two
> ubuntus directly.  

How?
For booting the correct kernel the grub in the mbr would have to know
which kernel to boot. And I can only manually update if I have two
different ubuntu installs being booted from this one grub. Thats the
thing I was asking about in the first place!

> And I'd probably not even bother installing the
> extra bootloaders to the partitions.  But if you do, you don't even
> need grub in the MBR; you can use the much simpler BSD bootloader
> which simply offers you a choice of partitions (or second disk) to
> boot from.

Sure I'd have to have a grub install for every ubuntu install if I want
an apt-get upgrade to automagically upgrade my config to boot an
upgraded kernel. Or is there an alternative to that?

kind regards Philip