One of the common practices when upgrading Microsoft Active Directory (AD) servers has been to perform a new installation of the Microsoft operating system and then upgrade the server as an AD server, perform an AD migration, and then upgrade the AD version on the new host. However, Microsoft has been offering upgrading locally for years, and it's best to use the upgrade locally when you don't have the additional hardware to install your new operating system anew. In some other cases, it may be easier to do the upgrade locally. In this post, we'll explore the pros and cons of upgrading locally vs. new installation, and we'll explain the steps you need to take to upgrade locally from Windows Server 2022 to Windows Server 2025.
Pros and Cons of Upgrading Locally
Let's explore the pros and cons of upgrading locally vs. new installation when working with DNS and Microsoft Active Directory roles.
Upgrade locally
Advantages:
- Retention of settings and data – Existing system settings, installed applications, and user data are preserved.
- Less downtime – The process is faster than a new installation, resulting in minimal service interruptions.
- Simpler process – It usually requires fewer steps and is less complex.
- Fewer compatibility issues – existing apps and services work properly after an upgrade.
Disadvantages:
- Old issues – There may be residual issues, additional files, and registry issues being moved from the old system.
- Need for compatibility checks – Need to thoroughly check compatibility before upgrading, as some apps may not be compatible with the new operating system.
- Upgrade Failure Risk – If the upgrade process fails, it may result in system instability or data loss.
New Installation
Advantages:
- Fresh Start – This method ensures that all previous system issues and incorrect configurations are removed.
- Optimal performance – You'll usually have a more stable and faster system as all old files and settings are deleted.
- Lack of old issues – Deletes problematic registry files and entries.
Disadvantages:
- Time-consuming – The process takes more time because you have to back up data, reinstall the operating system, reconfigure the settings, and reinstall the apps.
- Longer downtime – A longer process may result in longer downtime.
- More complexity – It's more complex than upgrading locally and requires more careful planning.
In our lab, we're upgrading our Domain Controller (DC) running on Windows Server 2022.
Pre-Upgrade Reviews
Now you can check out this link on Microsoft's site, which shows an older version of your operating system and the possibility of upgrading to Windows Server 2025. Before upgrading locally, you should check with your hardware manufacturer to see if an upgrade is possible on your hardware (if your system is physical). If your server is not physical and runs as a virtual machine in your local data center, simply perform a regular backup in case you want to revert to the previous state.
Tip: You can't use the Windows Server 2025 preview version to upgrade because this version doesn't allow your files, settings, and apps to be preserved.
Steps Before Promotion
Before you upload the ISO and start the upgrade by running the update.exe file, you'll need to do some checks and run commands to prepare Microsoft Forest and AD. Here's what Microsoft has recommended:
- Check the compatibility of Microsoft server applications
- Exploring the Requirements for Supporting Third-Party Programs
- Make sure your computer:
- It meets the hardware requirements of Windows Server.
- Not running on Azure.
In the PowerShell command prompt as an administrator, run the following command:
Get-WindowsFeature
This command is to view the roles and features installed on the host.
Run Forestprep and Adprep commands first
These two commands should be run on your first DC before starting the upgrade process (if your environment has more than one DC).
Tip: Yes, you should only run these commands on the first DC you upgrade. These commands should not be re-executed for any of the hosts you are upgrading.
Load the Windows Server 2025 ISO and go through the Command Prompt with administrator access to this directory:
D:\support\adprep
Tip: Let's assume that your CD-ROM drive is "D". In this directory, you will need to find an executable file called adprep.exe, which we will use to upgrade Forest and AD.
Enter the following command:
.\adprep.exe /forestprep
You will be informed that the AD forest schema is going to be upgraded and that the operation is irreversible. To confirm, type the letter C and press ENTER.
If there are no errors, run the following command as well:
.\adprep.exe domainprep
You should see the successful confirmation of this operation.
Upgrading locally from Windows Server 2022 to Windows Server 2025
Load the Windows Server ISO and run the setup.exe file in the ISO root directory. Right-click on the setup.exe file and select the Run as Administrator option.
Follow the installation process. You can just click NEXT, and the system will automatically search for updates and download them. If you don't want to do that, click on the "Change how Setup downloads updates" link and then you will have the option to not download updates at this time.
Select the version you want to upgrade to. In this example, I've chosen the Datacenter eval version with Desktop Experience.
Accept the EULA and select the "Keep files, settings, and apps" option. The process is quite simple; no one wants to keep anything, right?
A page will appear to display the information summary, and then you are ready to start the upgrade process.
The system performs the upgrade in the required amount of time that may vary. The duration of the upgrade depends on the size of the AD, the number of roles and apps installed, as well as the performance of the hardware you're upgrading.
After restarting, you will see different messages. The system will be rebooted several times during the process.
But in the end, everything will go well.
Post-Promotion Tasks
After the upgrade, you will need to check your AD structure as well as check the logs to make sure that the system does not have any issues associated with the upgrade. To do this, check the Event Viewer logs for the system, applications, and services.
You can also use the DCDIAG tool to test specific domain controller functions. With the DCDIAG command-line tool, you're essentially running a series of tests to diagnose the health and performance of your domain controllers.
Some of the key points to check out using DCDIAG include:
- DNS Function: Ensuring that your domain controller is identifiable in the DNS and that the DNS is working properly.
- Replication: Check the health of replication between domain controllers to ensure proper data synchronization.
- Connectivity: Check that the domain controller responds to ICMP pings and accepts LDAP connections.
- Roles and Services: Verifying the status and proper functioning of services and critical roles such as FSMO (Flexible Single Master Operations).
A detailed description of DCDIAG is beyond the scope of this post.
You can use the following command to check your DNS:
Dcdiag /test:dns
Performing the upgrade locally for Windows Server 2025 is an efficient method of migrating to the new version while maintaining your current configurations, applications, and data. By following the steps listed and best practices, you can minimize downtime. Keep in mind that careful preparation and planning is the key to success in promotions. Update your system and take advantage of the new features and improvements that Windows Server 2025 has brought you.
Upgrading locally is appropriate if time and resource constraints take precedence and there is no major problem with the current system. If you know that your host has already had issues like viruses or system files getting corrupted, the best option is to install a new one and reconfigure it. On the other hand, a new installation is ideal for ensuring a stable and optimized environment, especially if the current system has a lot of issues or needs a fresh start with new features.
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