Re: [Xen-users] Basic questions - numbered

[Ted Hilts <thilts@xxxxxxxxxxxxxxxx>]

Tim

Thankyou for your reply. Sorry that my question was confusing but sometimes
confused people ask confusing questions. I found this question very difficult
to word and would beg your indulgence if I am now too wordy.

To recap, you said:
I'm not sure what your question is, but the GrUB runes for booting Xen
are discussed in the Xen user's manual:
You referred me to:
title Xen 2.0 / XenLinux 2.6.9
  kernel /boot/xen.gz dom0_mem=131072
  module /boot/vmlinuz-2.6.9-xen0 root=/dev/sda4 ro console=tty0
  Question part 1 -- clarification: I was actually looking for comfirmation
on using  a group of logical partitions with each containing an install of
a Linux distribution such as SuSE, RH, DEB, etc.  

Also, instead of partitioning one of the six hardrives as  first primary,
second primary, third primary , and fourth primary partition (with extended
partition containing logical partions), I would only have  a first primary
(extended partition) with umteen  logical partions. with each of these logical
partitions containing an installed linux distribution. 

I realized that partioning this way is no problem but until recently I had
(mistakenly) always thought that linux had to be installed on a primary partition
on 0 (first) IDE 0 slot or the 1 (second) IDE 0 slot or the typical traditional
master locations. I did not realize that I could create linux installations
in logical partitions and refer and boot them on that basis.  I had always
used logical partitions for /boot, /usr, swap, and that sort of thing.  In
addition, I was under the impression that an extended partition having logical
partitions  had to be the last partition on a hard drive so if there were
two primary partitions the extended partition had to be last.  So if there
is only a primary partition with an extended partition having many logical
partitions it is the last as well as the first. 

Therefore, I had never attempted to create complete Linux installations within
a logical parition -- only parts of an installation  (like /boot, /usr, etc.)
that collectively defined the installation.

So, theoretically speaking,  if I were to use /dev/hde (the fith (5th) drive
-- in the sequence a, b, c, d, e, f,  if there were no gaps) I would have
 /hde1 and if on hde I allocated an extended partion with 64 logical partitions
(numbered 1 to 64) I could install a bootable (using Grub) linux distribution
in each of these logical paritions. 

BTW: I am trying to stay at a theoretical level but my question also comes
out of the situation with my current SuSE where I've actually got on the
6.4 SuSE install -- b and d missing leaving  (hda(hda1,hda2,hda3), hdc(hdc1,hdc3,hdc4),
hde, hdf, hdg, hdh, and a tape driveSeagate STT8000A ATAPI tied to (fd0)
floppy, hdi--DVD Samsung ATAPI, and finally hdj--HP CD+r/w).  This means
I have a,c,e,f,g,h,i,j accounting for all 8 IDE slots but apparently the
letter designation, as in hda, is not reserved but only follows the lettering
sequence.  So the 5th drive is desigated with "g". But I don't think this
variability is the case with Grub and the designations are reserved, as in
(hd4, n) which always refers to the 5th hard drive and a partition. The SuSE
Reference manual states that:
(hd0,0) is the first primary partition.
(hd0,1) is the second primary partition.
(hd0,2) is the third primary partition.
(hd0,3) is the fouth primary partition (usually an extended partition)
(hd0,4) is the first logical partition .
(hd0,5) is the second logical partition.

Thus my concern!!!  The numbering conventions seem to be static or fixed
which would make my GRUB sequence in the below line WRONG?   Just thought
you would like to know the basis of the question.

Continuing theoretically: If that drive contained just logical partitions
I would have on hde (hde1, hde2, hde3...hden) where n=1 to 64 -- I believe
0 refers to the extended partition itself but I am not sure as it is not
used just assumed.
And if this were translated into GRUB terminology I would have ((hd4,0),
(hd4,1), (hd4,2)...(hdn-1,n-1) where n =1 to 64
 
The above are my assumptions and I think I am WRONG in the above GRUB line???

Now the actual Question.

Question 2nd part: are these sequences correct for both Linux and Grub or
are the first 3  (Linux 1,2, 3, and Grub 0,1,2 ) "reserved numbers" making
my sequences incorrect for the 5th hard drive (having only an extended partition
with umteen logical partitions each containing an installed OS).

Thanks -- Ted. 


Tim Deegan wrote:
> Hi Ted,
>
> I have a few brief answers to some of your points below, to follow up
> from Mark:
>
> >  Then I tried it on two Linux machines (again that does not matter 
> > as it's a Live CD).  But the Live CD would not boot.  Ouch!!! After 
> > several days of testing I discovered (even though the bios was properly 
> > set so the CD should boot) that even an OS independent Smart Boot could 
> > not force the CD to boot nor even detect it. Even a SuSE CD self booting 
> > installation would not boot.
> >   
>
> Yep, sounds like your machines don't boot from CD-ROM.  Things that are
> worth trying in this situation:
>
> - SBM (Smart Boot Manager) floppy:  http://btmgr.sourceforge.net/download.html
> - GrUB floppy: http://www.gnu.org/software/grub/grub-legacy-faq.en.html#q4
>
> A floppy boot image for the demo CD is unlikely to happen because the 
> initrd the CD uses is significantly larger than will fit on a floppy. :)
>
> > If this seems feasible (moving a pre built Linux installation into a 
> > logical partition for this purpose) could I have an example of a GRUB 
> > configuration file as a kind of template for a dedicated multiple 
> > logical partitions boot???
> >   
>
> I'm not sure what your question is, but the GrUB runes for booting Xen
> are discussed in the Xen user's manual:
>
> http://www.cl.cam.ac.uk/Research/SRG/netos/xen/readmes/user/user.html#SECTION02240000000000000000
>  
> > Is the "grub.conf" file associated with the LIVE CD a good example of 
> > what I am looking for and how do I discover it's contents??? 
> >   
>
> The grub configuration on the CD is in /boot/grub/menu.lst on the CD; you
> should be able to read that file from a running system.
>
> > Can I do the following?
> >
> > "dd" the Live CD into one of these partitions mentioned above and boot 
> > to this "copy" on hard drive instead of CD???
> >   
>
> In theory, yes, but why would you?  The filesystem on the demo CD has a
> bunch of tweaks to make it run from CD (i.e. without writeable disks,
> and running several OSes from the same image).  Starting from that would
> give you something that's not quite a proper Debian install, and
> something that's not quite the proper Xen tools on top of it, which
> would just cause problems later on.
>
> Basically, the demo CD is intended to be just that: a demo.  It's *not*
> meant as a production platform.
>
> You would really be *much* better off installing a linux distro from
> scratch and then installing Xen into it.  Recent versions of Debian have
> excellent support for installing in difficult cases, and it sounds like
> your Suse install floppies work too.
>
>
> > That's how I read it. But this is where I am 
> > most confused because the Xen-based system has it's own bridge 
> > (assumedly to virtualize network connectivity) and I would think that 
> > each DomU or virtualization including Dom0 would also need a bridge to 
> > talk to my LAN machines or I've got this wrong and the bridges just join 
> > networks. (Sorry, but I am missing a bit of network insight here). 
> >   
>
> The demo CD doesn't use the network card of the machine.  Domain 0 talks
> to all the other domains via the 'xen-br0' bridge, which has the IP
> address 10.171.45.1.   You should be able to bring up real LAN
> interfaces separately with the usual linux tools.   You can then setup
> NAT between the inside (other domains via xen-br0) and the outside
> (LAN).  Read the man page for iptables for more details on how to do athat.
>
> Tim.



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