libvirt users - Oct 2017 - Re: error: internal error: missing backend for pool type 11 (zfs)

Hi all,

I'm trying to setup virt-manager with ZFS als storage on my Arch box. I
have created a pool named virt-pool and tried to use it as storage. First
with virt-manager and then in the terminal with virsh but I'm always
getting the following errors:



*virsh # pool-define-as --name zfsvirtpool --source-name virt-pool --type
zfserror: Failed to define pool zfsvirtpoolerror: internal error: missing
backend for pool type 11 (zfs)*

But ZFS seems to be working fine:

# zpool status
 pool: virt-pool
state: ONLINE
 scan: none requested
config:

       NAME                      STATE     READ WRITE CKSUM
       virt-pool                 ONLINE       0     0     0
         x                       ONLINE       0     0     0

errors: No known data errors

libvirt and VMM also. These are the installed versions:
Virtual Machine Manager v.1.4.3
virsh v.3.7.0
libvirtd (libvirt) 3.7.0

I have found that there was a bug last year which is supposed to be fixed:


*https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=827245
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=827245>*

So why I'm getting this error. Is something wrong with my setup?

Regards,
Nick
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On 10/02/2017 11:42 PM, Nick Gilmour wrote:
> Hi all,
> 
> I'm trying to setup virt-manager with ZFS als storage on my Arch box. I
> have created a pool named virt-pool and tried to use it as storage. First
> with virt-manager and then in the terminal with virsh but I'm always
> getting the following errors:
> 
> 
> 
> *virsh # pool-define-as --name zfsvirtpool --source-name virt-pool --type
> zfserror: Failed to define pool zfsvirtpoolerror: internal error: missing
> backend for pool type 11 (zfs)*
Your libvirt was built without support for ZFS. You need to contact your
distribution manufacturer and ask them to enable it. Or build libvirt on
your own.

However, as I am writing these lines I realized two things:

1) there's no API to query loaded drivers/storage backends.

2) storage backends are static. While we have libvirt drivers in
separate modules (.so files) and load them at start up, it's not the
same story with storage driver backends. These are hardcoded into the
storage driver. Might be worth it to have them dynamically loadable too.

Michal

@Michal: Thanks for your reply!

Indeed I have found a package in the AUR (libvirt-zfs) and only had to
change to the current version and add zfs-utils as dependency in the
PKGBUILD. Now I don't get the previous error anymore but I still cannot
setup a VM because I constantly get errors due to wrong permissions.

I have tried to change the permissions in:

   - /etc/libvirt/qemu.conf
   - /virt-pool/vmm
   - /dev/zvol/virt-pool


also:

# zfs allow <user> create,destroy,mount virt-pool/vmm

didn't help.

What are the correct permissions? Which user and group?

Nick


On Tue, Oct 3, 2017 at 8:44 AM, Michal Privoznik <mprivozn@redhat.com>
wrote:
> On 10/02/2017 11:42 PM, Nick Gilmour wrote:
> > Hi all,
> >
> > I'm trying to setup virt-manager with ZFS als storage on my Arch
box. I
> > have created a pool named virt-pool and tried to use it as storage.
First
> > with virt-manager and then in the terminal with virsh but I'm
always
> > getting the following errors:
> >
> >
> >
> > *virsh # pool-define-as --name zfsvirtpool --source-name virt-pool
--type
> > zfserror: Failed to define pool zfsvirtpoolerror: internal error:
missing
> > backend for pool type 11 (zfs)*
>
> Your libvirt was built without support for ZFS. You need to contact your
> distribution manufacturer and ask them to enable it. Or build libvirt on
> your own.
>
> However, as I am writing these lines I realized two things:
>
> 1) there's no API to query loaded drivers/storage backends.
>
> 2) storage backends are static. While we have libvirt drivers in
> separate modules (.so files) and load them at start up, it's not the
> same story with storage driver backends. These are hardcoded into the
> storage driver. Might be worth it to have them dynamically loadable too.
>
> Michal
>

On Tue, Oct 03, 2017 at 08:44:10 +0200, Michal Privoznik
wrote:
> On 10/02/2017 11:42 PM, Nick Gilmour wrote:
[...]
> 
> 2) storage backends are static. While we have libvirt drivers in
> separate modules (.so files) and load them at start up, it's not the
> same story with storage driver backends. These are hardcoded into the
> storage driver. Might be worth it to have them dynamically loadable too.
This was changed some time ago. Backends are loadable now:

src/.libs/libvirt_storage_backend_disk.so
src/.libs/libvirt_storage_backend_fs.so
src/.libs/libvirt_storage_backend_gluster.so
src/.libs/libvirt_storage_backend_iscsi.so
src/.libs/libvirt_storage_backend_logical.so
src/.libs/libvirt_storage_backend_mpath.so
src/.libs/libvirt_storage_backend_rbd.so
src/.libs/libvirt_storage_backend_scsi.so
src/.libs/libvirt_storage_backend_sheepdog.so
src/.libs/libvirt_storage_backend_vstorage.so
src/.libs/libvirt_storage_backend_zfs.so

Similarly to driver backends they are loaded at start of libvirtd.