[Qemu-discuss] Windows QEMU Guest Agent VSS Provider service stops during qemu backup

[Joop Martens]

Hi all,

 

I’m currently implementing the QEMU Guest Agent on all my KVM Windows guests.

I’m using the stable VirtIO drivers and Guest agent from Fedora: https://fedoraproject.org/wiki/Windows_Virtio_Drivers

Both the stable and latest release do provide Qemu Windows Guest agent 7.0.0.10.

 

After the Guest agent installation I initially received VSS events with ID 8194:

 

Volume Shadow Copy Service error: Unexpected error querying for the IVssWriterCallback interface.  hr = 0x80070005, Access is denied.

. This is often caused by incorrect security settings in either the writer or requestor process.

 

Operation:

   Gathering Writer Data

 

Context:

   Writer Class Id: {e8132975-6f93-4464-a53e-1050253ae220}

   Writer Name: System Writer

   Writer Instance ID: {6c777a34-53dd-4fb3-a4c9-b85d7e183e27}

 

I was able to fix this issue by adding local access permissions for the “Network Service” account at the Dcom security permissions:

 

On the client computer from the Start Menu, select Run

The Run dialog opens.

 

In the Open field type dcomcnfg and click OK.

The Component Services dialog opens.

 

Expand Component Services, Computers, and My Computer.

Right-click My Computer and click Properties on the pop-up menu.

 

The My Computer Properties dialog opens.

 

Click the COM Security tab.

Under Access Permission click Edit Default.

 

The Access Permissions dialog opens.

 

From the Access Permissions dialog, add the "Network Service" account with Local Access allowed.

Close all open dialogs.

 

Now an initial backup runs without any error but this is causing the QEMU Guest Agent VSS Provider service to stop running without any error in the event log.

As a result a second backup will cause an error: MSDTC Client 2 with event ID: 4879:

MSDTC encountered an error (HR=0x80000171) while attempting to establish a secure connection with system SERVERNAME.

 

This is probably caused because the QEMU Guest Agent VSS Provider service isn’t running anymore.

I can manually start the QEMU Guest Agent VSS Provider service but every backup is causing the service to stop.

 

I’m seeing this behavior at all my Windows based guests running both Windows Server 2012 R2 and Windows Server 2008 R2.

 

Since I can’t find any logging or troubleshooting possibilities for this particular service I would like to ask if somebody knows how to solve this issue or if anybody could explain how I could troubleshoot this issue to receive detailed information about the reason why this services stops running during a backup.

 

Thanks in advance and kind regards,

 

Joop