libvirt users - Apr 2020 - Re: libvirt remote uri format

Hi,

I am using python libvirt api to get domain information. When using a uri
without specifying the socket path,  an error occurs.

uri = "qemu+ssh://myuser@some.kvm.host/system"
conn = libvirt.open(uri)

This results in the following:

libvirt: XML-RPC error : internal error: received hangup event on socket

If I append the socket path to the URI, it works. e.g.

qemu+ssh://myuser@some.kvm.host/system?socket=/var/run/libvirt/libvirt-sock

Is this the recommended way to construct an ssh uri? My concern is that the
socket path may be different when connecting to different libvirt hosts.

remote host is ubuntu 20.04 running libvirtd (libvirt) 6.0.0 under systemd

- Joe

On Fri, 2020-04-03 at 19:37 -0500, Joe Muro wrote:
> Hi,
> 
> I am using python libvirt api to get domain information. When using a uri
without specifying the socket path, an error occurs.
> 
> uri = "qemu+ssh://myuser@some.kvm.host/system"
> conn = libvirt.open(uri)
> 
> This results in the following:
> 
> libvirt: XML-RPC error : internal error: received hangup event on socket
> 
> If I append the socket path to the URI, it works. e.g. 
> 
> qemu+ssh://myuser@some.kvm.host/system?socket=/var/run/libvirt/libvirt-sock
> 
> Is this the recommended way to construct an ssh uri? My concern is that the
socket path may be different when connecting to different libvirt hosts.
> 
> remote host is ubuntu 20.04 running libvirtd (libvirt) 6.0.0 under systemd
Is the client machine running macOS by any chance?

There is a long-standing issue where that platform will use different
paths for certain resources, including the libvirtd socket, and the
way it currently works is that the default socket path is chosen by
the client, so any mismatch will result in something like the above.

The plan is to replace our use of nc with a custom virt-nc helper
that will link against libvirt on the host side and will thus be able
to use the default socket path appropriate for the system; however,
as far as I'm aware nobody is currently working on it.

-- 
Andrea Bolognani / Red Hat / Virtualization

On Fri, Apr 03, 2020 at 07:37:19PM -0500, Joe Muro
wrote:
> 
> Hi,
> 
> I am using python libvirt api to get domain information. When using a uri
> without specifying the socket path,  an error occurs.
> 
> uri = "qemu+ssh://myuser@some.kvm.host/system"
> conn = libvirt.open(uri)
> 
> This results in the following:
> 
> libvirt: XML-RPC error : internal error: received hangup event on socket
> 
> If I append the socket path to the URI, it works. e.g.
> 
> qemu+ssh://myuser@some.kvm.host/system?socket=/var/run/libvirt/libvirt-sock
> 
> Is this the recommended way to construct an ssh uri? My concern is that the
> socket path may be different when connecting to different libvirt hosts.
Generally you should *not* need to specify the socket path. The libvirt
client will attempt to use the same socket path on the remote host, as
it would use on the source host.

Note that this assumes that libvirt was built with the same set of
--prefix, --localstatedir, --rundir options on both hosts. If that
is not the case, then the socket must be given explicitly.


Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

On Mon, Apr 06, 2020 at 10:45:49AM +0200, Andrea Bolognani
wrote:
> On Fri, 2020-04-03 at 19:37 -0500, Joe Muro wrote:
> > Hi,
> > 
> > I am using python libvirt api to get domain information. When using a
uri without specifying the socket path, an error occurs.
> > 
> > uri = "qemu+ssh://myuser@some.kvm.host/system"
> > conn = libvirt.open(uri)
> > 
> > This results in the following:
> > 
> > libvirt: XML-RPC error : internal error: received hangup event on
socket
> > 
> > If I append the socket path to the URI, it works. e.g. 
> > 
> >
qemu+ssh://myuser@some.kvm.host/system?socket=/var/run/libvirt/libvirt-sock
> > 
> > Is this the recommended way to construct an ssh uri? My concern is
that the socket path may be different when connecting to different libvirt
hosts.
> > 
> > remote host is ubuntu 20.04 running libvirtd (libvirt) 6.0.0 under
systemd
> 
> Is the client machine running macOS by any chance?
> 
> There is a long-standing issue where that platform will use different
> paths for certain resources, including the libvirtd socket, and the
> way it currently works is that the default socket path is chosen by
> the client, so any mismatch will result in something like the above.
> 
> The plan is to replace our use of nc with a custom virt-nc helper
> that will link against libvirt on the host side and will thus be able
> to use the default socket path appropriate for the system; however,
> as far as I'm aware nobody is currently working on it.
I've got patches which do most of the work, but need some polish and
refactoring still to make acceptable.

Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

The client machine is running macOS. So that explains it. For my case,
hard-coding the socket path is not a major problem, although having libvirt
"auto-detect" the correct path would certainly be nice.

Thanks for your help.

- Joe



From:	Andrea Bolognani <abologna@redhat.com>
To:	Joe Muro <joemuro@us.ibm.com>, libvirt-users@redhat.com
Date:	04/06/2020 04:47 AM
Subject:	[EXTERNAL] Re: libvirt remote uri format



On Fri, 2020-04-03 at 19:37 -0500, Joe Muro wrote:
> Hi,
>
> I am using python libvirt api to get domain information. When using a uri
without specifying the socket path, an error occurs.
>
> uri = "qemu+ssh://myuser@some.kvm.host/system"
> conn = libvirt.open(uri)
>
> This results in the following:
>
> libvirt: XML-RPC error : internal error: received hangup event on socket
>
> If I append the socket path to the URI, it works. e.g.
>
> qemu
+ssh://myuser@some.kvm.host/system?socket=/var/run/libvirt/libvirt-sock
>
> Is this the recommended way to construct an ssh uri? My concern is that
the socket path may be different when connecting to different libvirt
hosts.
>
> remote host is ubuntu 20.04 running libvirtd (libvirt) 6.0.0 under
systemd

Is the client machine running macOS by any chance?

There is a long-standing issue where that platform will use different
paths for certain resources, including the libvirtd socket, and the
way it currently works is that the default socket path is chosen by
the client, so any mismatch will result in something like the above.

The plan is to replace our use of nc with a custom virt-nc helper
that will link against libvirt on the host side and will thus be able
to use the default socket path appropriate for the system; however,
as far as I'm aware nobody is currently working on it.

--
Andrea Bolognani / Red Hat / Virtualization