[fedora-virt] What the heck are the guestfs-yaddayadda... virtual machines?

[Richard W.M. Jones]

On Sun, Jan 27, 2013 at 05:29:13PM -0500, Cole Robinson wrote:
> On 01/27/2013 04:44 PM, Tom Horsley wrote:
> > If I run virt-manager on fedora 18, I see random
> > instances of virtual machines named guestfs-something
> > pop up for a second, then go away.
> > 
> > Where the heck do they come from and why is it
> > happening?
> 
> If python-libguestfs is installed, virt-manager will use it in the background
> to determine guest OS and a few other interesting bits of info. Recently
> libguestfs grew the ability to do its magic using libvirt rather than a
> manually launched qemu instance. What you are probably seeing is those
> transient libguestfs appliances popping in and out of existence.
> 
> However I didn't think libguestfs was using libvirt by default on F18, and I
> didn't think it was connecting qemu:///system, so I'm not entirely sure what's
> happening. Are you using qemu:///session with virt-manager, or just the
> default libvirt connection?

Since Fedora 18, libvirt is now the default (but see below).

> Rich, any thoughts?

Well this is a bug / missing feature in libvirt.  When you create a
transient guest libvirt forces you to give it a name, and effectively
you have to give it a random name (because other instances of
libguestfs might be running at the same time).  So we give it a name
like guestfs-<random>, but that unfortunately means that a persistent
log file is created (probably under $HOME/.cache/libvirt/qemu/log),
and you see oddly named guests coming into existence.

We should fix this, but for now you could:

(1) Ignore the guests.

(2) Switch libguestfs to using the 'appliance' backend, which means it
directly runs qemu instead of using libvirt (this was the default
before Fedora 18):

  export LIBGUESTFS_ATTACH_METHOD=appliance

(3) Uninstall python-libguestfs.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org