John Howard - Senior Program Manager in the Hyper-V team at Microsoft

Senior Program Manager, Hyper-V team, Windows Core Operating System Division.

Hyper-V RC1 is available for download

Hyper-V RC1 is available for download

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Update: 26th June 2008. Hyper-V RTM is now available. RC1 is pre-release software. 



We're getting really close to shipping Hyper-V. Today, we can announce that RC1 is available.


If you're already running RC0, the upgrade is really simple. Unlike the Beta to RC0 update, virtual network configurations and virtual machine configurations are now compatible and are migrated in-place. The only gotcha to watch out for is that saved states are not compatible, which includes online snapshots. So please make sure online snapshots are deleted and merged, and your virtual machines are shutdown cleanly before applying the update.

If you are still running Hyper-V Beta, take a look at KB949222 for more information. Although that KB was written specifically for Beta to RC0 updates, the same overall information applies for Beta to RC1.

There is one thing in particular worth mentioning about RC1 - after the feedback you gave us in RC0 that upgrading the Integration Services for Windows Server 2008 virtual machines was inconsistent with all other operating systems, we listened. Starting with RC1, all virtual machines are equal in this regard. Simply run setup.exe from vmguest.iso (Actions/Insert Integration Services Setup Disk in Virtual Machine Connection) regardless of the virtual machine operating system. Note that you still need to apply the main update to the parent partition though!

The links are here:

Windows Server 2008 x64 (Apply this to the parent partition to upgrade to RC1). More info in KB950049.

And if you are using Windows Vista for Remote Management, here's the tools you need: (KB949587)   x64 and x86

RTM is getting closer! As always, I welcome your feedback about this release.



  • Rob - glad you got it sorted. The answer I did get back was:

    1. Log in as root.

    2. Execute the following commands as root:

    a. $ rmmod netvsc storvsc vmbus

    b. $ cp /boot/grub/menu.list.bak /boot/grub/menu.lst

    3. Follow the setup instructions as detailed in the read me.



  • Wally - you may be hitting a variation of in the initial update. However, not sure why it would be at 58% - 54% is what I would expect. Was that a typo?

    For the networking issue you are currently seeing, can you ne a bit more specific. Can you create virtual network switches? If so, are you saying that your VMs cannot access the network? Have you run the Integration Services setup inside the VM to get the RC1 drivers inside them?



  • The update from RC0 to RC1 went really smooth and the VM's seem to behave much better.

    The problem with Attesic NIC also seems to be gone with RC1 =)

  • Hello Again,

    So I highly doubt that you want to hear this again but it looks like a variation of the "You do not have the requested permission to complete this task. Contact the administrator of the authorization policy for the computer ‘COMPUTERNAME’" error with a new name.

    So I am running Windows Vista Business SP1 (x64) and I just installed Hyper-V RC1 on my servers (Very nice and simple install with no problems, THANK YOU) and Hyper-V RC1 Management Console on my Vista workstation. I get the following error when trying to connect to one of my servers: "Access denied. Unable to establish communication between 'SERVERNAME' and 'WORKSTATIONNAME'"

    I am added to the local administrators group on the servers and it recognizes me as an admin in all other forms of remote management, just not Hyper-V. All computers are on the same domain. I have two Hyper-V servers running Server Core clustered together and I cannot access either. I can access Hyper-V on both of them using a full install of Server 2008 on a different computer.

    Any Ideas this time around?


    Ryan Lenkersdorfer

    Washington State University

  • Please, GOD, say we don't have to remove the virtual nics in the next release.  This is a nightmare for remote administrators...

  • I updated to RC1 and I've noticed I no longer have driver support for x64 legacy network adapters in my guests. I use the legacy adapter for deploying purposes (from SCCM), which is how I noticed in the first place (task seqeunce failed)

    Kind regards,

    Ward J

  • Ward - there is no change in repect of legacy network adapters in RC1. You're more likely seeing an incompatibility between RC1 and SCVMM. Rakesh has some more information on his SCVMM blog entry here:



  • Thomas - no, that should not be necessary. Unfortunate as it was, the breaking change was a penalty of using pre-release software and necessary to ensure support once we reach RTM.



  • Hi John,

    Your Beta to RC0 guide absolutely saved my skin on a critical server when that came out - I had blindly just applied to the update without any precautions!

    Anyway, that experience, which was nerve-racking to say the least, has made very wary.  Can you just clarify the steps for updating to RC1 from RC0 - particularly with regard to Integration Services for Windows Server 2008?  My understanding is this (where I have a single VM and single parent);

    1. Install RC1 update on guest virtual machine

    2. Shutdown VM

    3. Delete saved states for VM

    4. Install RC1 on parent

    5. Reboot

    6. Start VM

    All done?  What about Integration Services for Windows Server 2008 - what do I need to do there, what is it's function (sorry, but I'm still pretty new to VM's)...


    3. Delete snapshots

  • Hey John,

    I recently rebuilt my machine and found that beta version of Hyper=V worked without a problem.  The after I downloaded the RC1 code and installed it, I am being told that Hyper-V failed to launch.  I am seeing this as a problem on a lot of the forums.  Anything you have heard about?

    Thanks in advance.

  • How can I confirm the version of Hyper-V that I am running?  e.g. what's the registry key that I should be looking for?

  • Dave

    No, not quite.

    1. Shutdown VM

    2. Delete saved states

    3. Delete snapshots, wait for merge to complete.

    4. Install RC1 and reboot as needed

    5. Start VM

    6. Install ICs in VM by running setup.exe from vmguest.iso which is inserted into the virtual CD/DVD drive using the actions/insert integration services setup disk from Virtual Machine connection.

    Running that setup.exe updates the appropriate drivers for synthetic device support in the virtual machine, as well as the integration components such as heartbeat, shutdown etc.



  • MichaelVC. Yes, we are aware of a bug in RC1 which affects the Hypervisor from launching correctly on a small number machines. The class of machine is where there is more than one physical socket containing processors, and the processors are reporting mismatching capabilities. However, that fix will not be available until a future release. Is there anything in the system event log during machine boot which indicates a Hypervisor failure? If so, can you post back the error message for me to confirm if you are hitting the same problem.



  • Michael - easiest way is to look at the version number of one of our drivers (eg \windows\system32\drivers\hvboot.sys). I'm not in front of a Hyper-V machine right now, and it's been so long since I used RC0 that I'm struggling to recall the build number <gulp> but IIRC, it was 18004. RC1 is 18010.  Beta was pre-18000 which is the build number of Windows Server 2008 RTM, and stretching my memory, it was 17119 for our bits.

    If you need a registry key, take a look at a Hyper-V enabled box, and do a search in the registry for one of the above numbers. There should be plenty of files in the registry with that number which you could equally well use for a check. We don't have an explicit registry key as such.

    A third way would be to use WMI to query for QFEs installed on the machine eg "wmic qfe get hotfixid". Always look for the latest QFE. If 950049 is listed, you have RC1. If 949219 is installed, you have RC0 (assuming 950049 which superceeds it is not present). If neither are listed, you are on beta (Windows Server 2008 RTM). Of course, I can't disclose future KB numbers though :)

    Hope that helps,



  • The RC1 release of Hyper-V ( KB950049 ) hit Windows Update yesterday. For more information on Hyper-V

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