NFS with nearby host, VM clients?

[Michael Jinks]

Much thanks.  Any of these would (will) be just fine.  I have at least one
question.

ssh port forwarding would be the easiest, it was one way I tried, but I'm
missing something.  In your example:

>   ssh -R 10809:nbd-server:10809 vm

...is that to say that 10809 is the only port we need to handle?  Or, is it
just an example showing one of the necessary ports?

NFS+RPC is one of my holdups; 10809, Linux Network Block Devices, is in
/etc/services on some, not all, of my Linux hosts, so, please educate me:
does that process fix the "RPC problem"?

Thanks.





On Wed, Apr 20, 2022 at 9:47 AM Richard W.M. Jones <rjones at redhat.com>
wrote:

> On Mon, Apr 18, 2022 at 11:22:07PM -0500, Michael Jinks wrote:
> > I have a laptop, running VMM, with a handful of VM's.  Next to that, I
> have a
> > pile of disks running on ZFS, and I'd like to give the VM's network
> access
> > there, for running backups or whatever.
> >
> > The holdup is that the laptop (pop-OS if that matters -- so Ubuntu, so
> Debian)
> > automatically prohibits any outside network traffic to the VM's.
> > Self-contained outward traffic from the VM is fine, like ssh; but the
> outside
> > host can't see in to any VM, so, for instance, when the VM tries to
> NFS-mount
> > to the outside, the rpc connection back will fail.
> >
> > In the past, my way of allowing something like this was to make a new
> virtual
> > network running on the host, visible for the VM's and reachable by the
> outside
> > service, but I haven't been able to find how to do that in a modern VMM
> setup.
> > I can find, in the GUI:
> >
> >   QEMU/KVM - Connection Details -> Virtual Networks: "Create a
> > new virtual network"...
> >
> > ...but everything I've tried has failed in one way or another.  Maybe I
> just
> > don't know how to set that up?
>
> I used this relatively recently.  It's still a lot more painful to set
> up than it really needs to be however ...
>
>
> https://wiki.libvirt.org/page/Networking#Bridged_networking_.28aka_.22shared_physical_device.22.29
>
> Another option is just port forwarding.  Pretty sure you can set this
> up from virt-manager, but if not you can definitely do it through
> editing the libvirt XML:
>
> https://libvirt.org/formatdomain.html#channel
>
> virsh edit is described here:
>
> https://www.redhat.com/sysadmin/virsh-subcommands
>
> Another option would be attaching a remote disk to the guest.  Again,
> not sure if this can be done in virt-manager, but it's certainly
> possible from libvirt XML:
>
> https://libvirt.org/formatdomain.html#hard-drives-floppy-disks-cdroms
>
>   <disk type='network' device='disk'>
>     <driver name='qemu' type='raw'/>
>     <source protocol='nbd'>
>       <host name='nbd-server'/>
>     </source>
>     <target dev='vda' bus='virtio'/>
>   </disk>
>
> Another, even simpler option is a reverse SSH tunnel, ie something
> like this on the host:
>
>   ssh -R 10809:nbd-server:10809 vm
>
> That will export the NBD port on nbd-server:10809 into the VM, so you
> would be able to access an NBD server from inside the VM.
>
> Rich.
>
> > I understand the security concerns, and won't have a problem flatting
> that
> > down.
> >
> > If I'm just not looking in the right docs, please point me in the
> > right direction.
> >
> > Or, if I'm going about this some unwise way, please educate me.
> >
> > Thanks.
> >
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
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> build Windows installers. Over 100 libraries supported.
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>
>
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