Migrating existing groups from Commons 2.x to Commons 3 I've just installed Commons 3 on a sandbox server and am curious where to begin migrating groups data over. I realize this is may also apply generic D6 to D7, but is there additional consideration for a Drupal Distribution? What steps should I take to move content and groups from Common 2.x to Commons 3.x?

That is, how can I move existing groups from Commons 2.x into Commons 3.x that will include content types attached to those groups (discussions, postings, events, wikis)? 

I know that Activity Streams are different between these versions and we can live with out that, but I'd like to bring over content attached to the appropriate groups and users.
Commons maintainer japerry is in a team that created 
Commons Migration module exactly for your task.

Posted by nateswart on March 18, 2013 at 9:46pm
Provide a migration path from Commons 2.x to 3.x

It uses Migrate with Drupal-to-Drupal data migration to get the job done. Sadly, it's still in early development, and according to this feature request not quite finished yet. But at the very least you can see in code what approach original developers use.