can't share uploads
Fragment of a discussion from Project:Support desk
Note, if you own both wikis, using foreignAPIRepo is a bit inefficient. See Manual:$wgForeignFileRepos#Using_files_from_a_database_that_you_can_access_:_ForeignDBRepo for how to set up sharing of uploads the more modern way. manual:$wgUseSharedUploads is the older method. $wgSharedUploadDirectory is the path where the images are actually stored on the server.
In regards to Mlpearc's post, it should be noted that it's technically unnessary to have both $wgUseInstantCommons on, and use a foreignAPIRepo for 'pedia, since foreignAPIRepo'ing wikipedia will also get you commons (otoh, it might still be a good idea, since there's a bug involving fetching descriptions from nested foreign repos)
