libvirt users - Jul 2014 - Acces to hypervisor from a KVM guest

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.
So, I run  virsh and the run hostname command.( got that in virsh help :  ....
hostname                       print the hypervisor hostname ....)
Unfortunately, I got following error when starting virsh :

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)

Do I miss to install some package on my KVM guest ? or is it not the right way
to get this information ?

Any help is welcome.

Thx.

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

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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