[Pkg-libvirt-maintainers] Bug#805624: Bug#805624: libvirt-bin: document how to access host file system

[Guido Günther]

On Thu, Nov 26, 2015 at 05:36:39PM +0530, Ritesh Raj Sarraf wrote:
> On Thu, 2015-11-26 at 11:26 +0100, Guido Günther wrote:
> > So in this case s.th. like:
> > 
> > * How can I mount a directory from the host in a QEMU VM.
> > 
> >   Use the 9pfs filesystem with a domain xml like:
> > 
> >     <filesystem type='mount' accessmode='passthrough'>
> >       <source dir='/direcgory/on/host'/>
> >       <target dir=share'/>
> >     </filesystem>
> > 
> >   and to mount it within the guest use:
> > 
> >   cat <<EOF > /etc/fstab
> >       share /mnt/share  9p  trans=virtio,rw,_netdev 0       0
> >   EOF
> >   mount /mnt/share
> >      
> >   See https://libvirt.org/formatdomain.html#elementsFilesystems for
> >   details.
> > 
> 
> This is pretty good.
> 
> > Or maybe we want to have more like a "How do I switch from VirtualBox
> > to
> > QEMU" section?
> > 
> 
> I'd rather stick with documenting basic obvious things only. I think
> the catch is on what constitutes "basic obvious things".
> 
> 
> > What I'd like to understand is what motivated you to submit the
> > patch.
> > I'm pretty sure we need to improve on the docs, just trying to figure
> > out _where_.
> 
> So, virt-manager, shows the option to add a share. There, in that
> window, it gives no feedback on what needs to be done on the guest.
> 
> So the standard expectation would be that on next boot the guest would
> have the storage accessible. FYI, that's how it is on VBox (Assuming
> you have the VBox Guest Extensions Installed).
> 
> So with nothing being accessible in the Guest VM, my next step was to
> look at the maintainer docs (README.Debian), if anything obvious is
> documented.
> 
> Next, Google for "libvirt mount hostfs" led to a bunch of blog entries
> that gave me the hint about 9p file system.
> 
> Assuming, that there may be users who may not have access to the
> internet, this is not the most optimal option.
> 
> 
> 
> But that said, I do think too, that there needs to be a line ensuring
> we don't clutter our usual README docs.
> 
> 
> 
> 
> Looking again at this stack:
> 
> libvirt-bin package has no direct relationship with libvirt-doc.
> Neither does virt-manager package.
> 
> virt-manager GUI app has a Help menu. But just with 1 button talking
> "About" the tool.
> 
> 
> Actually, you put the right question on what led me to write the patch.
> So in my case, the usual practice has been to refer README.Debian. But
> while writing this reply, it has made me wonder what a normal user
> would do. Because there is no direct relationship established in-
> between the tool and the documentation; even though both are available
> in Debian.

Hmmm...so how would we go from here? Looking from the VBox->KVM
migration for "desktop" scenarios this would need improvements in
virt-managers help system or even better: make things simpler by using
qemu-ga to actually add a mount point for the 9pfs filesystem.  We seem
to have more than enough in  qemu-ga nowadays to make this possible:

   https://github.com/qemu/qemu/blob/master/qga/qapi-schema.json

We have such nice tools but sometimes we lack the plumbing to make
things simple.

Cheers,
 -- Guido