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Re: [Xen-devel] Hotplug scripts not working... xen/ia64 domU stopped working

On Fri, Dec 02, 2005 at 09:41:39AM -0800, Magenheimer, Dan (HP Labs Fort 
Collins) wrote:

> Problem identified but it's a weird one!  I turned on logging
> in /etc/xen/scripts/block and /etc/hotplug/xen-backend.agent
> using Adam's cool trick of redirecting stderr output (exec 2>>file),
> and discovered I *was* getting a message that domain0 already
> was using the loopback device.
> So I again tried turning on w! in /etc/xen/xmdefconfig
> and this time it worked!
> However, when I turned off logging, the w! no longer makes
> the problem go away, and there is a long pause before the
> "Error: Device 769... Hotplug scripts not working" message.
> (Logging need only be enabled in xen-backend.agent to
> make the problem again go away.)
> Some weird timing problem?

Possibly.  I've checked some code in today to serialise checks here, so that
may well make the problem go away, but since you are only using one block
device, it seems to me that there might be an underlying problem.  You ought to 
get a proper error message rather than "scripts not working".  I would guess
that the script's bailing out before managing to write the "hotplug-status" node
in the store, but if that goes away when you're not logging, that's a little

Anyway, I'd be inclined to try the new changesets (not yet pushed to the public
tree) and see if that improves things. 

> My /etc/xen/xmdefconfig is very short:
> kernel = "/tmp/xenlinux"
> memory = 256
> nics=0
> disk = ['phy:loop0,hda1,w']  # <-change to w!
> and after a fresh boot, I am simply doing:
> # lomount -t ext2 -diskimage /var/xen/hda /mnt
> # xend start
> # xm create
> I can see how it could be interpreted that loop0 is
> being used both by domain0 and the newly created domain,
> but isn't this a common use model?

Only if you want to corrupt your filesystem!  Writing to that file via /mnt
in dom0 and via /dev/hda1 in the guest ought to corrupt your fs nicely.


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