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I upgraded my Windows 2008 Hyper-V host server to Windows 2008 R2 last night. The upgrade went smoothly, but when it settled down as the new version, I found two virtual machines out of seventeen to be missing from the Hyper-V console UI.

From the Hyper-V event log i see

Log Name: Microsoft-Windows-Hyper-V-VMMS-Admin Source: Microsoft-Windows-Hyper-V-VMMS Date: 6/4/2011 2:31:26 AM Event ID: 16300 Task Category: None Level: Error Keywords: User: SYSTEM Computer: elune Description: Cannot load a virtual machine configuration: General access denied error (0x80070005) (Virtual machine ID 5185AC13-4148-4AFE-9024-6E74FE3C9754) Event Xml: <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"> <System> <Provider Name="Microsoft-Windows-Hyper-V-VMMS" Guid="{6066F867-7CA1-4418-85FD-36E3F9C0600C}" /> <EventID>16300</EventID> <Version>0</Version> <Level>2</Level> <Task>0</Task> <Opcode>0</Opcode> <Keywords>0x8000000000000000</Keywords> <TimeCreated SystemTime="2011-04-05T18:31:26.432942100Z" /> <EventRecordID>641</EventRecordID> <Correlation /> <Execution ProcessID="1964" ThreadID="2064" /> <Channel>Microsoft-Windows-Hyper-V-VMMS-Admin</Channel> <Computer>elune</Computer> <Security UserID="S-1-5-18" /> </System> <UserData> <VmlEventLog xmlns:auto-ns2="http://schemas.microsoft.com/win/2004/08/events" xmlns="http://www.microsoft.com/Windows/Virtualization/Events"> <VmName> </VmName> <VmId>5185AC13-4148-4AFE-9024-6E74FE3C9754</VmId> <ErrorMessage>%%2147942405</ErrorMessage> <ErrorCode>0x80070005</ErrorCode> </VmlEventLog> </UserData> </Event>

These "missing" VMs do not have any online snapshots tied to them. Even for those that did I removed and merge the snapshots based on Microsoft's advice, and they've "survived".

There seem to be a lot of "General access denied error (0x80070005)" discussion when it comes to starting virtual machines. But my case is the Hyper-V service being unable to even load the configuration, so Hyper-V knows where those VM config locations but don't have permission to access them?

The three Hyper-V services are launched with LOCAL SYSTEM account, and the "Virtual Machines" folders for those VMs do grant Full Control permissions. What I observe from the other VMs is their folders have additional ACEs for Virtual Machines group and the VM GUID itself?

enter image description here

I tried to duplicate this ACE structure, but Windows cannot locate the GUID principals of those missing VMs. What would be causing this problem?

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  • I don't know what is causing the issue you are having and maybe this is obvious but you can easily recreate the VMs in Hyper-V Manager assigning the same resources (CPU, memory, NIC, etc) that were there before and just point the new VMs at the existing .vhd files and be back up in minutes. Commented Apr 6, 2011 at 7:10
  • yes, that is a possible workaround. however i am interested in investigating the details that influence these aspects. Commented Apr 6, 2011 at 8:07

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Well, this is a strange means.

The key thing is Windows/Hyper-V is referring to a "list" somewhere to tell it what virtual machines are registered with the server. My virtual machines are scattered across multiple drives, so there has to be a centralised repository. Which turns out to be

C:\ProgramData\Microsoft\Windows\Hyper-V\Virtual Machines

there are symbolic links that refer to the physical locations of the actual config XML files. I noticed the troubled VM links had a "lock" icon. enter image description here

I edited the security ACL of the troubled symbolic link. Sure enough it does not have the NT Virtual Machine account like the rest, so instead I granted it Full Control to the Users group. Restarted Hyper-V Virtual Machine Management service, and it could once again load up the missing VMs. It appears to work without the Virtual machine accounts.

Still haven't gotten the complete deep answers I was looking for to explain just what Hyper-V is requiring out of those Virtual machine accounts, but at least the original virtual machine config can be reused.

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