| Started PUT "/api/operatingsystems/1" for 2001:4800:7818:101:be76:4eff:fe04:7fb2 at 2015-06-24 08:11:58 +0000
2015-06-24 08:11:58 [app] [I] Processing by Api::V2::OperatingsystemsController#update as JSON
2015-06-24 08:11:58 [app] [I] Parameters: {"operatingsystem"=>{"config_template_ids"=>["58"]}, "apiv"=>"v2", "id"=>"1"}
....
2015-06-24 08:11:59 [app] [W] Action failed | ActiveRecord::UnknownAttributeError: unknown attribute: config_template_ids | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/attribute_assignment.rb:88:in `block in assign_attributes' | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/attribute_assignment.rb:78:in `each' | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/attribute_assignment.rb:78:in `assign_attributes' | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/persistence.rb:215:in `block in update_attributes' | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/transactions.rb:295:in `block in with_transaction_returning_status' | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction' | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/transactions.rb:208:in `transaction' | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/transactions.rb:293:in `with_transaction_returning_status' | /opt/rh/ruby193/root/usr/share/gems/gems/activerecord-3.2.8/lib/active_record/persistence.rb:214:in `update_attributes' | /usr/share/foreman/app/controllers/api/v2/operatingsystems_controller.rb:61:in `update'

Reproducible e.g. with hammer command

hammer os add-config-template --id 1 --config-template tpl59