Xen users - Jul 2008 - dom0 console weirdness (reboot the only fix I''ve found)

hey ya''ll! so I''ll try to be as detailed as possible here.
basically my xm
console is getting corrupt somehow and the only fix I''ve found is a
reboot.
(lame)

first, the details..

[root@oak-dev-xen001 ~]# cat /etc/redhat-release
CentOS release 5 (Final)

[root@oak-dev-xen001 ~]# rpm -qa | grep -i xen | sort
kernel-xen-2.6.18-8.1.15.el5.x86_64
kernel-xen-2.6.18-8.el5.x86_64
xen-3.0.3-25.0.4.el5.x86_64
xen-libs-3.0.3-25.0.4.el5.x86_64

[root@oak-dev-xen001 ~]# uname -a
Linux oak-dev-xen001 2.6.18-8.1.15.el5xen #1 SMP Mon Oct 22 09:01:12 EDT
2007 x86_64 x86_64 x86_64 GNU/Linux

(i''ve been able to reproduce this behaviour with both kernels listed
above)

****

I''m creating my (very basic) VM as follows:

dd if=/dev/zero of="foo" bs=1048576 count=1 seek=20480 &>
/dev/null
mkfs.ext3 -qF foo
mount -o loop foo /mnt/xen

for i in console null zero mem port core full ram tty hda; do
    MAKEDEV -a -d /mnt/xen/dev $i
done

yum -t -e 0 -y --installroot=/mnt/xen install kernel

****

my config file (left out networking foo to just get the thing to boot):

[root@oak-dev-xen001 ~]# cat /etc/xen/configs/foo
name = "foo"
vif = [ '''', ''bridge=xenbr0'' ]
disk = [ ''file:/data/xen/disks/foo,hda1,w'' ]
kernel = "/boot/vmlinuz-2.6.18-8.el5xen"
ramdisk = "/boot/initrd-2.6.18-8.el5xen-no-scsi.img"
memory= 1024
root = "/dev/hda1 ro"
extra = "4 enforcing=0"
on_crash = ''destroy''

****

NOW...the weird part.

''xm create -c /etc/xen/configs/foo'' just hangs the console (no
response) and
eventually it exits with:
  Error: destroyDevice() takes exactly 3 arguments (2 given)

I tail the dom0 logs while starting up the domU and nothing stands out as
erroring. once I corrupt the xen console via this method I can''t boot
ANY of
my VMs -- even the ones I know are working. they all exit with the same
error/blank console as above and require a reboot of the dom0 in order to
boot successfully. once I reboot, I drop into the xen console without
problem upon my next ''xm create'' -- my VMs boot and everything
works as it
should.

mind you this -only- occurs during new VM creation via the above
''dd/yum
install'' method above. prior to corrupting my console, I can copy
existing
VMs/start them up without incident - it''s just the ''dd/yum
install'' method
that screws things up and prevents me from starting up any of my VMs.

my hypothesis? I think something confuses the dom0 during my VM creation,
but I''m not sure where. my guess is the yum install.

TIA

j


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> hey ya''ll! so I''ll try to be as detailed as possible
here. basically my xm
> console is getting corrupt somehow and the only fix I''ve found is
a reboot.
> (lame)
Boo, that''s not a great problem for you to be stuck with!  Have you
tried a
xend restart?  Is that not enough? :-/
> first, the details..
>
> [root@oak-dev-xen001 ~]# cat /etc/redhat-release
> CentOS release 5 (Final)
>
> [root@oak-dev-xen001 ~]# rpm -qa | grep -i xen | sort
> kernel-xen-2.6.18-8.1.15.el5.x86_64
> kernel-xen-2.6.18-8.el5.x86_64
> xen-3.0.3-25.0.4.el5.x86_64
> xen-libs-3.0.3-25.0.4.el5.x86_64
>
> [root@oak-dev-xen001 ~]# uname -a
> Linux oak-dev-xen001 2.6.18-8.1.15.el5xen #1 SMP Mon Oct 22 09:01:12 EDT
> 2007 x86_64 x86_64 x86_64 GNU/Linux
>
> (i''ve been able to reproduce this behaviour with both kernels
listed above)
>
> ****
>
> I''m creating my (very basic) VM as follows:
>
> dd if=/dev/zero of="foo" bs=1048576 count=1 seek=20480 &>
/dev/null
> mkfs.ext3 -qF foo
> mount -o loop foo /mnt/xen
>
> for i in console null zero mem port core full ram tty hda; do
>     MAKEDEV -a -d /mnt/xen/dev $i
> done
I think you need an xvc0 / hvc0 node in here for the Xen console device, 
depending on what kernel you''re using.  For a RHEL kernel, I think
it''s xvc0.
> yum -t -e 0 -y --installroot=/mnt/xen install kernel
>
> ****
>
> my config file (left out networking foo to just get the thing to boot):
>
> [root@oak-dev-xen001 ~]# cat /etc/xen/configs/foo
> name = "foo"
> vif = [ '''', ''bridge=xenbr0'' ]
> disk = [ ''file:/data/xen/disks/foo,hda1,w'' ]
> kernel = "/boot/vmlinuz-2.6.18-8.el5xen"
> ramdisk = "/boot/initrd-2.6.18-8.el5xen-no-scsi.img"
> memory= 1024
> root = "/dev/hda1 ro"
> extra = "4 enforcing=0"
> on_crash = ''destroy''
>
> ****
Have you tried including an explicit "console=xvc0" or somesuch in the
extra=
setting?
> NOW...the weird part.
>
> ''xm create -c /etc/xen/configs/foo'' just hangs the
console (no response)
> and eventually it exits with:
>   Error: destroyDevice() takes exactly 3 arguments (2 given)
That looks like a Xend bug, which is probably fouling up Xend for all your 
other domains as well :-(
> I tail the dom0 logs while starting up the domU and nothing stands out as
> erroring. once I corrupt the xen console via this method I can''t
boot ANY
> of my VMs -- even the ones I know are working. they all exit with the same
> error/blank console as above and require a reboot of the dom0 in order to
> boot successfully. once I reboot, I drop into the xen console without
> problem upon my next ''xm create'' -- my VMs boot and
everything works as it
> should.
>
> mind you this -only- occurs during new VM creation via the above
''dd/yum
> install'' method above. prior to corrupting my console, I can copy
existing
> VMs/start them up without incident - it''s just the
''dd/yum install'' method
> that screws things up and prevents me from starting up any of my VMs.
Interesting.  I guess it must be something about your setup there then - are 
you able to boot the "known good" domains with otherwise the same Xen
config
as the "known bad" setup (i.e. same kernel, initrd, etc)?
> my hypothesis? I think something confuses the dom0 during my VM creation,
> but I''m not sure where. my guess is the yum install.
You''re correct about dom0 getting confused.  It''s something
exploding in Xend
but I''m not 100% sure why.

Cheers,
Mark

-- 
Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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