In this chapter, we will introduce the Marionette Collective (MCollective). We will have a look at the architecture of MCollective, which includes a message broker. We will examine the configuration of ActiveMQ, the preferred message broker for MCollective. We'll also learn how to diagnose issues with ActiveMQ. Then, we'll explore the MCollective command line utility, mco. Finally, we'll look at problems with time synchronization, network access, and logging.