If you don't follow this, you might get in trouble just as I did.
STSAdm.exe -o installfeature -filename "HR_MetaData\Feature.xml"
STSAdm.exe -o activatefeature -filename "HR_MetaData\Feature.xml" -url "http://MySite/sites/humanresources"
The error message:
"Unknown Error"If you have turned off custom Errors in Sharepoint you should see the following error:
Object reference not set to an instance of an object.You will see the errors above when navigating to Site Actions -> Site Settings -> Site Columns;
at Microsoft.SharePoint.ApplicationPages.FieldListRenderer.Render(HtmlTextWriter output)
or navigate to: http://MySite/sites/HumanResources/_layouts/mngfield.aspx
When you deploy a feature using STSAdm -url make sure you take into consideration the case of the URL.
After using the correct case everything worked beautifully.
STSAdm.exe -o activatefeature -filename "HR_MetaData\Feature.xml" -url "http://MySite/sites/HumanResources"