app/views/images/form/_docker.html.erb
<%= text_f f, :username, :value => @image.username || "root", :help_inline => _("The user that is used to ssh into the instance, normally docker-user, ubuntu, root etc") %>
<%= password_f f, :password, :help_inline => _("Password to authenticate with - used for SSH finish step.") %>
<%= image_field(f) %>
<%= checkbox_f f, :user_data, :help_inline => _("Does this image support user data input?") %>