Windows Server 2012 Migration Guides.

By using the migration tools, administrators can migrate certain roles, features, shares, operating system settings, and other data from the source server to the destination server running Server 2012.

There is no single procedure for migrating all the Windows Server roles. Instead, Microsoft provides detailed migration guides for individual roles, and sometimes for individual role services within a role.

Up-to-date migration guides are available at the Windows Server Migration Portal at the
Windows Server 2012. Link