libvirt users - Jul 2014 - follow-up to thread : Acces to hypervisor from a KVM guest, ( by the way , how to enter a follow up in a thread ?) Thx

Hi,

This is what I tried :

Y , how enter    an answer in the thread ?)

virsh -c qemu+ssh://127.0.0.1:22/system  hostname
root@127.0.0.1's<mailto:root@127.0.0.1's> password:

error: End of file while reading data: : Input/output error

error: failed to connect to the hypervisor



In another hand ,as we have few information  to share ,  I was thinking to use a
virtio channel to dialog between host and guest .

Does it fit ?



Thx



J.P. ?



-----Message d'origine-----

De : Eric Blake [mailto:eblake@redhat.com] Envoyé : vendredi 4 juillet 2014
15:20 À : Jean-Pierre Ribeauville;
libvirt-users@redhat.com<mailto:libvirt-users@redhat.com> Objet : Re:
[libvirt-users] Acces to hypervisor from a KVM guest



On 07/04/2014 04:23 AM, Jean-Pierre Ribeauville wrote:
> Hi,
>
>>From a KVM guest, I want to retrieve  the hostname of the host on which
the hypervisor is running.
> Before doing that by using libvirt API, I first try via virsh.


Well, virsh just uses the libvirt API under the hood.  I'd suggest that you
try: virsh -c qemu://host/system hostname



except that this is a chicken-and-egg situation, because virsh in the guest
doesn't know what host to connect to.



If you are using the out-of-the-box NAT setup, then you could use
qemu://192.168.122.1/system, since your guest will be using an IP address
assigned from that subnet from the host.



Other than that, libvirt is not really designed for guest-to-host communication,
but for host management of guests.  You'll have to solve your problem in
some other way.  Consider the same situation with bare metal hosts - if you are
provisioning a cluster, and want machines in the cluster to communicate to a
particular controller, but not all machines connect to the same controller, how
would you do that?  If you can solve that problem, then you can use it to solve
your guest provisioning problem.


> error: Failed to reconnect to the hypervisor
> error: no valid connection
> error: internal error Unable to locate libvirtd daemon in /usr/sbin
> (to override, set $LIBVIRTD_PATH to the name of the libvirtd binary)


This failure is because you did not use -c to connect to a remote daemon, but
don't have libvirtd running in the guest.  You do not need libvirtd running
locally to use virsh for remote connections, but you do need to know where the
remote connection lives.



--

Eric Blake   eblake redhat com    +1-919-301-3266

Libvirt virtualization library http://libvirt.org




[cid:image001.png@01CF75CE.35F97F50]

Jean-Pierre RIBEAUVILLE
Developer
Tel: 01 49 11 45 81

Discover Systar's
Videos!<https://www.youtube.com/channel/UCvyaJkMXCGFo8_XZYd9rcBw>

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On 06.07.2014 16:45, Jean-Pierre Ribeauville wrote:
> Hi,
>
> This is what I tried :
>
> Y , how enter    an answer in the thread ?)
>
> virsh -c qemu+ssh://127.0.0.1:22/system  hostname root@127.0.0.1's
> <mailto:root@127.0.0.1's>password:
>
> error: End of file while reading data: : Input/output error
>
> error: failed to connect to the hypervisor
The I/O error seems like either libvirtd or ssh {client,server} died. Do 
you happen to know/find out which one of these it has been?
>
> In another hand ,as we have few information  to share ,  I was thinking
> to use a virtio channel to dialog between host and guest .
Correct. virtio channels are designed just for having a bidirectional 
pipe into the guest to feed an app running within the guest with some data.

Michal

On 07/06/2014 08:45 AM, Jean-Pierre Ribeauville wrote:
> Hi,
> 
> This is what I tried :
> 
> Y , how enter    an answer in the thread ?)
If you aren't already subscribed to the list, it is possible to use
gmane to reply to a conversation while keeping it properly threaded:

http://news.gmane.org/gmane.comp.emulators.libvirt.user


It is a general shortcoming of the mailman 2 engine that we use for this
list, that the mailman web interface does not provide an easy way to
request either a correctly-threaded mailto: reply URL, or a way for an
older message be resent (mailman3 and the hyperkitty interface are
supposedly trying to rectify this, and other things, but they still
aren't ready for general use).  If you don't have the original mail, but
still want your reply to be threaded correctly, the current approach is
rather tedious of manually figuring out the correct In-Reply-To: header
to add to your mail by browsing the .mbox archives:
https://www.redhat.com/archives/libvirt-users/
https://www.redhat.com/archives/libvirt-users/2014-July.txt.gz
and if that didn't make any sense to you, then don't worry about it.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org