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Hyper-V Mounting and Sharing ISO Files

As we spent time on the Self Service portal for Virtual Machine Manager, we will continue to exercise the ability to use some ISOs for booting the VMs directly, and I often publish these resources to their console. However it was not long before they reported a horrible message which needed a little reading to figure out

**Error (12700)
**VMM cannot complete the Hyper-V operation on the HYPER-V.host server because of the error: ‘MY-VM’ failed to add device ‘Microsoft Virtual CD/DVD Disk’. (Virtual machine ID 2A82C375-BBC3-429D-8568-F41453538AC5)

_‘MY-VM’: User account does not have permission required to open attachment ‘FileServer.HostISOsNIXCentOS5.4CentOS-5.4-x86_64-bin-DVD.iso’. Error: ‘General access denied error’ (0x80070005). (Virtual machine ID 2A82C375-BBC3-429D-8568-F41453538AC5)
(Unknown error (0x8001)) _

Recommended Action
Resolve the issue in Hyper-V and then try the operation again.

If any of you have ever tried to mount a ISO on Hyper-V Host A while using the console from Hyper-V Host B, you will recognise this message in a different form.

The Solution

So, the fix is not to difficult, some additional steps are required for each Hyper-V Host deployed, and the Library Servers

Library Server

The server which will host the ISO files been shared for use by the Hyper-V nodes is generally considered as the Library server (this is also the term used in SCVMM). The following step Must be repeated for each new Hyper-V Server added to the environment, AND for each Library server which will be utilized by the Hyper-V Server.

On each server with the shared ISO folder (Library Servers):

  1. Set the NTFS permissions to Full for the Hyper-V computer Account.
  2. Set the Share permissions to FULL for the Hyper-V computer Account.

Active Directory Delegation

Once each Hyper-V server on has been set up, the following series of steps need to happen before the Hyper-V server will be allowed to mount a network share. If these steps are not done, Hyper-V will throw a “General access denied error” whenever an attempt is made to mount a network located ISO in a VM.

This delegation will be using Constrained Delegation to remotely manage a server running Hyper-V that uses CIFS/SMB file shares.

On a domain DC:

  1. Open Active Directory Users and Computers
  2. Find the Hyper-V server computer object and double click on it.
  3. Click the Delegation tab.
  4. Click **on **Trust this computer for delegation to the specified services only radio button.
  5. Click the Use any authentication protocol radio button.
  6. Click the Add button.
  7. Click the Users or Computers… button.
  8. In the Add Services dialog box, click Users or Computers, enter the name of each library server that stores ISO image files, and then click OK.
  9. Click on the cifs Service Type and click the OK button.
  10. Click the Apply and OK buttons.

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Once the above two procedures have been accomplished, allow replication to complete. Reboot the Hyper-V box if it still gives the General Access Denied error. Once complete the ISO should mount in the VM via the Hyper-V Manager with no problems.

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