How to Demote (Remove) a Domain Controller

After you have installed new domain controllers there comes a moment when you need to remove or better said, demote the old domain controller. Old domain controllers can’t just be simply turned off, they need to be properly removed from the domain.

In some cases though, you might not have access anymore to the old domain controller. In this case, we can still demote the domain controller. Only we will need to use a different method for it.

In this article, I will explain both methods to demote a domain controller. The steps below can be used for Windows Server 2008r2 and newer, including Windows Server 2022.

Preparing the domain

Before we can demote the domain controller we will need to check the following points to ensure a smooth transition and avoid any issues:

• Check replication – We need to make sure that the replication between the old and new domain controller is running without any error. Use the command repadmin /replsummary <new-dc-name> to check for any errors.
• DHCP and DNS – If the old domain controller is also running DHCP and DNS, make sure that these services are also transferred to the new domain controller
• DNS on clients – Ensure that the DNS records on the clients (and other servers) are pointing to the new domain controller. Otherwise, they won’t be able to log in
• Create a Backup – Create a full backup of the old domain controller and verify the backup. This way you can always restore the server in case of any issues

FSMO roles will be transferred automatically when you demote the domain controller. You can check where the FSMO roles are running with the command netdom query FSMO.

Demoting an active Domain Controller

If you still have access to the domain controller then we can easily remove the domain controller using the Server Manager. Make sure that you have checked the points above before you continue.

Verify the Removal of the Domain Controller

Now the old domain controller is removed, we will need to make sure that everything is running smoothly. On the new domain controller, open the console and run the command dcdiag. This will check the health of your domain controller and will show any errors.

If you have two or more domain controllers left, then run the command repadmin /showrepl to verify that the replication between the remaining domain controller is running without any errors.

Demote a Domain Controller with PowerShell

We can also use PowerShell to demote the domain controller. Instead of clicking through 9 screens, you can remove the domain controller with a couple of commands:

# Import the ADDSDeployment module
Import-Module ADDSDeployment

# Demote the server
Uninstall-ADDSDomainController -DemoteOperationMasterRole:$true -RemoveDnsDelegation:$true -Force:$true

# Run the following command after the reboot to remove the Active Directory Sites and Services
Uninstall-WindowsFeature AD-Domain-Services -IncludeManagementTools

Manually Remove a Domain Controller

We can also manually remove a domain controller. Is step is only recommended to use when you don’t have access anymore to the server.

1. Open Active Directory and Services on the active domain controller
2. Open the Domain Controllers OU
3. Delete the old domain controller
4. Click Yes

5. Select Delete this Domain Controller anyway
6. Click on Delete
7. Confirm it one last time by clicking on Yes

The last step is to remove the server from the Active Directory Sites and Services:

• Open the Active Directory Sites and Services from the start menu
• Expand Sites > Default-Fist-Sites-Name > Servers
• Right-click on the old domain controller and choose Delete

If the old domain controller also had a DNS role, then we also need to remove the server from the Name Servers in the DNS Manager.

1. Open the DNS Manager on the active domain controller
2. Expand Forward Lookup Zones
3. Right-click on your domain and select properties
4. Open the Name Servers tab
5. Delete the old server from the names server

Also, delete the Name Server record from the domain DNS zone and any subfolder.

Wrapping Up

Demoting a domain controller isn’t that difficult anymore since Windows Server 2008r2. A lot is done on background these days automatically, like transferring the FSMO roles and cleaning up the metadata.

The recommended method to remove the domain controller is using the Server Manager or PowerShell. Only use the manual method if you really can’t access the server anymore.

I hope you found this article useful, if you have any questions, just drop a comment below.