RE: auto-installing debian on xen on debian withdebian-installer preseeding

RE: auto-installing debian on xen on debian withdebian-installer preseeding

[James Harper]

Does the debian installer really not support lvm? I'm sure I've
installed debian with root on software raid + lvm before... maybe the
sarge version has less features than the one I used, although this was
between 3 and 6 months ago.

I'd use debootstrap in preference to the debian installer, but that's
probably just my preference, the installer might make the final config a
bit easier.

James



> -----Original Message-----
> From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-
> bounces@lists.xensource.com] On Behalf Of Philip Hands
> Sent: Wednesday, 29 June 2005 22:07
> To: Debian Install System Team; xen-devel@lists.xensource.com
> Subject: [Xen-devel] auto-installing debian on xen on debian
withdebian-
> installer preseeding
> 
> Hi Folks,
> 
> Hopefully this will be of interest to some of you.
> 
> I've put together a debian-installer preseed setup, that allows (among
> other things) one to do a non-interactive install of Xen with a
minimal
> Debian as it's Domain0, sets up LVM so that one can create disks for
other
> domains and then lets you run the debian installer in a new domain so
that
> you can then install Debian instances.
> 
> For the Xen folks, this should turn into an easy way for people to dip
> their toe in the water without having to read lots of tedious
> documentation, and also be a pretty decent way of doing real
deployments
> (although I'd have thought that using debootstrap for the secondary
> installs might make a bit more sense, but at least you get a machine
where
> you can do that without any effort)
> 
> For the debian-installer folks, you might be interested (or horrified
;-)
> about how I managed this with only slight tweaking to the sarge
release
> version of debian-installer (given that it doesn't support LVM, so I
had
> to
> do a bit of scripting).  Also, there's some (at present rather
kludgey)
> tweaks that are needed to allow debian-installer to work within an
> unprivileged xen domain.
> 
> Given that you could have a load of diagnostic tools in Dom0, and then
> fire
> up one or more installs in subsequent domains, with the (theoretical)
> possibility of monitoring what they were doing from the outside, this
> could
> turn into a nice environment for testing debian-installer.  Although
at
> present it's significantly less helpful than a real machine because I
> don't
> see any way of getting to /dev/tty[234] under xen, so debugging is
> currently a right pain,
> 
> Anyway, here it is:
> 
>   http://hands.com/d-i/
> 
> There are some HOWTOs and top page includes a README.html.  It's still
a
> work in progress, so I may well reorganise the layout of the
> subdirectories
> at some point (it's mildly chaotic at present).  The idea behind the
> structure is that one can turn up to a site with standard(ish) boot
media,
> and have the preseed system determine the site it's running on (or you
can
> tell it by hand) and then install the requested machine type.
> 
> The xen setup described above will get installed if you specify a
machine
> type of "xen0", which you do by booting the mildly tweaked boot media,
and
> specify this at the boot prompt:
> 
>   boot:  auto26 local/cfg=xen0
> 
> the tweaks to the boot media are described in the
HOWTO-{PXE,CD,USB}.txt
> files, the details about the xen setup are described in the
HOWTO-xen.txt
> 
> If people want to customise this to their own needs, they can either
grab
> a
> copy and point the install media at their local server in the initial
> preseed,cfg, or they're welcome to have write access to the svk
repository
> where all this resides (once I work out a clean way of admin-ing
that).
> 
> Anyway, feel free to have a play, and I'm very open to suggestions on
how
> to improve things.
> 
> Things that are currently less than perfect:
> 
>   Xen:  it would be nice to know how to access the other virtual
consoles
>         of a XenU domain from Dom0, so one could get at the shell if
an
>         install goes wrong.
> 
>   debian-installer:
>       the current setup uses side effecting include-commands in a
>       positively abusive manner to set preseed variables under
scripted
>       control --- there must be a better way (or we should add one)
> 
>       I'd like to be able to say "include this preseed file if it
exists,
>       but don't give me an error if it doesn't" or alternatively
"include
>       this file if it exists, otherwise include that one"
> 
>       It would be nice to have a script run late enough in the
base-config
>       so that one could reboot (in this case for the first boot into
Xen)
> 
> Cheers, Phil.
> 
> P.S.  Please only reply to one list unless you're pretty sure that
you're
>       saying something of interest to both.

Re: auto-installing debian on xen on debian withdebian-installer preseeding

[Philip Hands]

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James Harper wrote:
> Does the debian installer really not support lvm?

It does for interactive installs, but the automated partitioner
(partman-auto) doesn't unless partman-auto-lvm is also installed, and
that's not the case in the sarge debian-installer release version.

It's possibly the case for the latest development branch, but getting this
auto installation stuff working is fiddly enough without building it on
moving foundations.

> I'm sure I've installed debian with root on software raid + lvm before...

by hand, it's not a problem.

> I'd use debootstrap in preference to the debian installer, but that's
> probably just my preference, the installer might make the final config a
> bit easier.

The main reasons for doing it this way are:

  because someone suggested it, and it seemed a suitably sick idea ;-)

  because it means that one can develop an auto installer preseed recipe
  for normal machines, and then use that to install a xen domain, or vice
  versa.

  it might end up being useful as a test environment for debian-installer

  it decouples the versions of software needed on dom0 and the target new
  domain.  One can imagine a machine installed with xen now being left
  on a particular reliable set of software, but installing the latest
  bleeding edge stuff into a new domain --- doing this without needing to
  upgrade deboottrap in dom0 might be useful at some point.

I'm not certain that any of these are of real interest to normal Xen users,
but adding something to the end of the xen0 auto installer, that
debootstraps Debian or even installs RedHat, NetBSD etc, on a bunch of new
subdomains, would not be too hard, and could well be quite useful.

Cheers, Phil.


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