I am using devise and recently added active admin, which created a separate table of admin_users to keep admins.
All works fine with Active Admin when I try to log i
In config/initializers/active_admin.rb
you can add the following:
config.skip_before_action :authenticate_user!
You can also use the DSL provided to modify the ActiveAdmin controller: http://activeadmin.info/docs/8-custom-actions.html#modify_the_controller
Note: For Rails versions before 5.0 you will want to use skip_before_filter
.