# File lib/phusion_passenger/config/utils.rb, line 40
        def select_passenger_instance
                if pid = @options[:instance]
                        @server_instance = AdminTools::ServerInstance.for_pid(pid)
                        if !@server_instance
                                puts "*** ERROR: there doesn't seem to be a #{PROGRAM_NAME} instance running on PID #{pid}."
                                list_all_passenger_instances(AdminTools::ServerInstance.list)
                                puts
                                puts "Please pass `--instance <#{PROGRAM_NAME}> PID>` to select a specific #{PROGRAM_NAME} instance."
                                abort
                        end
                else
                        server_instances = AdminTools::ServerInstance.list
                        if server_instances.empty?
                                abort "*** ERROR: #{PROGRAM_NAME} doesn't seem to be running."
                        elsif server_instances.size == 1
                                @server_instance = server_instances.first
                        else
                                complain_that_multiple_passenger_instances_are_running(server_instances)
                                abort
                        end
                end
        end