[xen-tools-dev] xen-tools4.2rc

[Dmitry Nedospasov]

Hey guys,

On Wed, Aug 25, 2010 at 02:12:44PM +0200, Axel Beckert wrote:
> > I'm actually the person who persuaded Steve to get some pygrub and
> > iscsi support into xen-tools.
> 
> IIRC there's no iscsi support yet. Can you outline what would be
> necessary to get iscsi support into xen-tools?

I run iscsi now via lvm, i.e. I have vms on top of an lvm on top of
iscsi. Though I like the idea of adding iscsi support in general. The
only problem that i see, is creating the disk image for the iscsi
volume, assuming you're not connecting to a localhost iscsi (which
you're not).

If the only support that you are looking for is for xen-tools to connect
to an existing iscsi device with a username and password, then format
that iscsi disk and booting it (probably as phy:// in the VM .cfg), then
that shouldn't be too hard to do and I'll take a look at it.

I have to admit though, that I'm not a super experienced iscsi user. I
think that running a Physical Volume/Volume Group, hosting 10-20 Logical
Volumes (which are the disk images) on top of an iscsi disk is better
than running 10-20 iscsi disks. Right now the default configuration sets
up 2 disks per machine (root and swap). Running one disk per machine
does seam reasonable though, however we'll probably need to expand the
functionality of our "partitions" feature, to be able to partition an
iscsi disk.

I'm just curious to hear from you, Michel, how you would imagine this
working for you. Like i said, i recently moved to iscsi and I'm quickly
starting to migrate lots of things to it, so I sincerely want to hear
your use-case.

Your question made me think of the following scenario: I run a xen vm
for a long time, now I want to boot it on some physical desktop. and
this is easy to do thanks to iscsi. Nice!

> > So you might imagine I'm happy to see
> > that being maintained. Anyways.. I think you made xen-tools to
> > automagically include kernel and module packages when --pygrub's in
> > the xen-create-image command. Just wondering if i'm correct in
> > assuming that and how far that goes..
> 
> If I remember correctly this is true. I Cc'ed our xen-tools developer
> mailing list (http://xen-tools.org/mailman/listinfo/xen-tools-dev) so
> all of the xen-tools devs can have a look at it (therefore also the
> nearly full quote), especially Dmitry who wrote that part.

I can answer this one. Pygrub boots a kernel on the guest machine. Hence
you need to install a kernel onto the guest machine for pygrub to boot,
otherwise it crashes and burns (actually just gives you an error, but I
wanted to say crash and burn).

I'm actually going to be improving the kernel that gets installed in the
next couple of weeks, when we finally start moving to what we devs call
the "-common" scripts :)

> > BTW ; I stumbled across some bugs.
> > When tty and sda are set in xen-tools.conf and one installs with  
> > --pygrub, pygrub, securetty and fstab are mixed up a bit. For example  
> > you might get /dev/sdaX in fstab but /dev/xvdaX in /boot/grub/menu.lst.  
> > Squeeze and Lucid never boot with a console if tty is in xen-tools.conf.  
> > They work perfectly after changing some stuff to hvc after install time  
> > though.
> 
> Ok, we'll have a look at it.

Oops :) I can believe that one!

> > Besides all that.. THANK YOU for picking up on xen-tools!! :)
> 
> :-)

:) I told Axel this story. I caught my fellow admins trying to patch-in
pygrub and lucid support into 3.9 last night. Then I said, "Guys theres
a new upstream with all those features", "but how do you know?", they
asked, and I said "Because I wrote it and commited it" :)

All the best,

D.
-- 
Dmitry Nedospasov <dmitry at nedos.net> -- Twitter: @nedos
Web: http://nedos.net -- Github: http://github.com/nedos