Connect the serial port module cable to this connector, then install the module to a slot opening at the back of the system chassis. Introduction to Linux - A Hands on Guide This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter. Having a problem logging in? Page 32 The system may become unstable or may not boot up if the power is inadequate. Turn OFF the computer and unplug the power cord. If an error is found , the LED next to the error device will continue lighting until the problem is solved.