Katello is not actually a single product in isolation, but a union of several open source infrastructure management products into one cohesive infrastructure management solution. Where Pulp is solely focused on the efficient, controllable storage of packages (and other important content for infrastructure management), Katello brings together the following:

• Foreman: This is an open source product designed to handle the provisioning and configuration of both physical and virtual servers. Foreman includes a rich web-based GUI, a RESTful API, and a CLI tool called Hammer, providing a rich and varied means of management. It also provides integration with several automation tools, originally just Puppet but more recently also Ansible.
• Katello: Katello is actually a plugin for Foreman and provides additional features such as the rich version control of content (more so than Pulp alone) and subscription management.
• Candlepin: Provides software subscription management, especially integration with environments such as the Red Hat Subscription Management (RHSM) model. Although it is possible to mirror Red Hat repositories in Pulp, the process is cumbersome, and you risk violating your license terms because there is no visibility on the number of systems you are managing or their relationship to your Red Hat subscriptions.
• Pulp: This is the very same Pulp software that we explored in the last chapter, now integrated into one fully featured project.
• Capsule: A proxy service for distributing content and controlling updates across a geographically diverse infrastructure while maintaining a single management console.

The use of Katello hence provides several advantages over using Pulp alone, and even if you use it just for patch management (as we will explore in this chapter, in the section entitled Patching with Katello), the rich web GUI, CLI, and API lend itself to integration with enterprise systems. Beyond this though, Katello (and more specifically Foreman, which underpins it) provides many other benefits such as being able to dynamically PXE boot servers and control both container and virtualization systems, and it can even act as both the DNS and DHCP servers for your network. Indeed, it is fair to say that the combination of Katello/Foreman is designed to sit at the heart of your network, although it will only perform the functions you ask of it, so those with existing DNS and DHCP infrastructures need not fear.

It is worth mentioning that Katello also features tight integration with the Puppet automation tool. The original project was sponsored by Red Hat, and before their acquisition of Ansible, Red Hat and Puppet had a strategic alliance, which led to it becoming heavily featured in the Katello project (which is available commercially as Red Hat Satellite 6). Given the Ansible acquisition, while the Puppet integration still remains in Katello, support for integration with Ansible, especially through Ansible Tower/AWX, has evolved rapidly and it is entirely up to the user which automation tool they wish to use.

At this stage, the venerable Spacewalk software tool deserves an honorable mention. Spacewalk is the upstream open source version of Red Hat Satellite 5 and is still being actively developed and maintained. There is a huge degree of overlap between the two systems in terms of high-level functionality; however, Katello/Satellite 6 is a complete from-the-ground-up rewrite of the platform and so there is no clear upgrade path between the two. Given that Red Hat's contribution to the Spacewalk program is likely to decrease when they end-of-life their Satellite 5 product, our focus in this book will be on Katello. 

Indeed, it is fair to say that Katello deserves a book of its own, so rich is its feature set. Our goal in this chapter is simply to raise awareness of the Katello platform and to demonstrate how it lends itself to patching in an enterprise environment. Many of the additional features, such as the PXE booting of servers, require an understanding of the concepts we have already covered in this book, and hence it is hoped that, should you decide upon Katello or Satellite 6 as a platform for managing your infrastructure, then you will be able to build on the foundation that this book provides and explore additional resources to take you further.

Let's get started by taking a practical look in the next section at how to install a simple standalone Katello server so that we can explore this more fully.