in dev mode (on localhost .. not tested in production  w
Passenger;.) , it seems I still need to clear the temp file in my
action code....  wo this line it crashes w the usual error "Can't dump
file" upon the redirect ... with the line it runs well..

thanks for your feedback

  def change_avatar
    @partner = Partner.find(params[:id])
    @partner.update_attributes(:avatar => params[:partner][:avatar])
    params[:partner][:avatar].tempfile = nil unless params[:partner]
[:avatar].tempfile.nil?
    redirect_to backoffice_partner_url(@partner)
  end