S4B – Error preparing forest.

Was installing a Skype for Business server the other day, and the simple task of preparing the forest failed. I am always on the alert when doing Active Directory forest wide tasks as prepare schema and prepare forest, so it is not fun to see error messages during these tasks.

prepareforestWhat now. It is no good feeling to see “Unrecoverable” and “You cannot retry this operation”. But I had to retry, and then there was a slight different error message.

prepareforest2I’ve had errors before, and at those cases the simple thing to do was to change from  “Local domain” to “Domain FQDN” in the “Universal Group Location” dialog box.


This time there was nothing but lots of scary errors.

I know this domain has several trusts configured, so it looks like the wizard get confused of where to  put these groups. Next step was to run prepare forest from PowerShell so that I was able to provide all this information to the command.

Enable-CsAdForest -GroupDomain s4b.local -GroupDomainController s4b-dc1.s4b.local -GlobalCatalog s4b-dc1.s4b.local

And finally success. The command completed without warnings and errors.