1. Normally, i'm not a fan of in-place upgrades, but...it depends on organization requirements. A clean install with scripted configurations is always better. 2. Here is the lazy way for those who have no choice... 3. Snapshot the VM (VMware, Hyper-V, KVM...whatever it is). 4. Add the iSO to the VM (Don't bother booting from the BIOS and running the ISO that way). It will just tell you to boot into the OS anyway. (thank you Microlazy) 5. Open a CMD or Powershell as an administrator. 6. Adprep is now located under "support\adrep\" on the 2019 disk. ( Domain Controllers Only ) 7. From the CLI run the following: adprep.exe /forestprep and then click "C" 8. Domain prep: adprep.exe /domainprep /domain yourdomain.com 9. Next upgrade the GPO Domains: adprep.exe /domainprep /gpprep /domain yourdomain.com 10. Now run the upgrade installer or relaunch it and "Continue where I left off" 11. If it barks about space. Don't add. R