Create the Key Distribution Services KDS Root Key
This article for the IT professional describes how to create a Microsoft Key Distribution Service (kdssvc.dll) root key on the domain controller using Windows PowerShell to generate group Managed Service Account passwords in Windows Server 2012 or later.
Domain Controllers (DC) require a root key to begin generating gMSA passwords. The domain controllers will wait up to 10 hours from time of creation to allow all domain controllers to converge their AD replication before allowing the creation of a gMSA. Waiting up to 10 hours is a safety measure to prevent password generation from occurring before all DCs in the environment are capable of answering gMSA requests. Trying to use a gMSA too soon might fail when the gMSA host attempts to retrieve the password, as the key may not have been replicated to all domain controllers. gMSA password retrieval failures can also occur when using DCs with limited replication schedules or if there's a replication issue.
Note
Deleting and recreating the root key may lead to issues where the old key continues to be used after deletion due to caching of the key. The Key Distribution Service (KDC) should be restarted on all domain controllers if the root key is recreated.
Membership in the Domain Admins or Enterprise Admins groups, or equivalent, is the minimum required to complete this procedure. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.
Note
A 64-bit architecture is required to run the Windows PowerShell commands which are used to administer group Managed Service Accounts.
To create the KDS root key using the Add-KdsRootKey cmdlet
On the Windows Server 2012 or later domain controller, run the Windows PowerShell from the Taskbar.
At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:
Add-KdsRootKey -EffectiveImmediately
Tip
The Effective time parameter can be used to give time for keys to be propagated to all DCs before use. Using Add-KdsRootKey -EffectiveImmediately will add a root key to the target DC which will be used by the KDS service immediately. However, other domain controllers will not be able to use the root key until replication is successful.
KDS root keys are stored in Active Directory in container CN=Master Root Keys,CN=Group Key Distribution Service,CN=Services,CN=Configuration,DC=<forest name>;. They have an attribute msKds-DomainID that links to the computer account of the Domain Controller that created the object. When this domain controller is demoted and removed from the domain, the value will refer to the tombstone of the computer account. You can ignore the broken value as it is only used to help the administrator track the object when it's freshly created. You may also change the attribute value and point it to the computer object of another domain controller in your forest.
For test environments with only one DC, you can create a KDS root key and set the start time in the past to avoid the interval wait for key generation by using the following procedure. Validate that a 4004 event has been logged in the KDS event log.
To create the KDS root key in a test environment for immediate effectiveness
On the Windows Server 2012 or later domain controller, run the Windows PowerShell from the Taskbar.
At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:
$a=Get-Date
$b=$a.AddHours(-10)
Add-KdsRootKey -EffectiveTime $b
Or use a single command
Add-KdsRootKey -EffectiveTime ((get-date).addhours(-10))