[libvirt-users] Migration hangs on Gentoo with KVM

[Eric Blake]

[re-adding the list]

On 08/01/2011 04:22 PM, Jonathan Stoppani wrote:
>
> On Aug 1, 2011, at 16:20 , Eric Blake wrote:
>
>> On 08/01/2011 04:11 PM, Jonathan Stoppani wrote:
>>> Hi there,
>>>
>>> I'm trying to migrate a domain between two Gentoo hosts using KVM as hypervisor, but the migration hangs.
>>> I tried both live or offline migration modes without success.
>>
>> Does your 'nc' command have a -q option?  If so, then this is probably
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=726174
>>

>
> Thanks for the prompt answer Eric! Yes, nc has a q option:
>
>   -q, --hold-timeout=SEC1[:SEC2]   Set hold timeout(s) for local [and remote]

Glad to hear that we found root cause to your problems, then.

>
> The bug specifically refers to ssh, does that mean that it should work over tcp?

The problem is that libvirt is trying to start a remote nc session over 
ssh; but looking at http://libvirt.org/remote.html, it looks like ssh is 
the only protocol using nc in that manner (so yes, you can probably 
avoid the issue by using tcp or tls).  Meanwhile, I think you can work 
around it without patching libvirt, by using this as your remote URI:

qemu+ssh://user@remotehost/system?netcat=/path/to/nc-wrapper

where nc-wrapper is an executable script installed on remotehost, 
looking like:

#!/bin/sh
exec /path/to/real/nc -q0 "$@"

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org