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Users who update their PCs via Windows Update (for Business) have long received both monthly cumulative updates and feature updates via the Unified Update Platform.
However, the implementation of the UUP for WSUS and SCCM has been delayed by years. It is currently available as a public preview and should be generally available in the first quarter of 2023. Once it is, all updates for Windows 11 22H2 and later will be delivered to WSUS and SCCM in this format.
Add MIME types via IIS Manager
For WSUS to be ready to receive UUP updates, admins must add two MIME types to the Internet Information Services (IIS). This can be done via the GUI of the IIS Manager.
If you are running WSUS on Server Core, you must first enable remote management for IIS and install IIS Manager for Remote Administration on the client.
After connecting to the server, click the MIME Types icon.
This opens a list of all registered MIME types. Select the Add command from the context menu, and enter .wim as the file name extension and application/x-ms-wim as the MIME type in the form.
Repeat this procedure for the .msu extension to which you assign application/octet-stream.
Registering MIME types from the command line
As an alternative to the IIS Manager, you can use the appcmd.exe utility to register MIME types. In the first step, it is recommended to check whether the two file extensions are already assigned to a MIME type. The following PowerShell command does the job:
. $Env:WinDir\system32\inetsrv\appcmd.exe list config /section:staticContent | select-string "(wim|msu)"
Under cmd.exe, the corresponding command looks like this:
%SystemRoot%\system32\inetsrv\appcmd.exe list config /section:staticContent | findstr /i "wim msu"
If entries are present and configured incorrectly, remove them in PowerShell with
. $Env:WinDir\system32\inetsrv\appcmd.exe set config /section:staticContent /-"[fileExtension='.msu']" . $Env:WinDir\system32\inetsrv\appcmd.exe set config /section:staticContent /-"[fileExtension='.wim']"
Then, you can register the two MIME types like this:
. $Env:WinDir\system32\inetsrv\appcmd.exe set config /section:staticContent /+"[fileExtension='.msu',mimeType='application/octet-stream']" . $Env:WinDir\system32\inetsrv\appcmd.exe set config /section:staticContent /+"[fileExtension='.wim',mimeType='application/x-ms-wim']"
To check, invoke appcmd again, as above, with the list parameter.
Microsoft will soon make the UUP available for on-prem systems like WSUS and SCCM. For WSUS servers to get these updates, you need to register two MIME types.
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For this purpose, the IIS Manager GUI is available. However, it must first be enabled for remote administration, if required. Alternatively, you can use the appcmd.exe program on the command line, especially on Server Core.