Infrastructure as Code, 2nd Edition

Chapter 12. Managing Changes to Servers

Many organizations and teams focus on processes and tools to build servers and other infrastructure, but neglect changes. When a change is needed—to fix a problem, apply security patches, or upgrade software—they treat it as an unusual event. If every change is an exception, then you can’t automate it. This mindset is why so many organizations have inconsistent, flaky systems. It’s why many of us spend our time switching between picking up dull tickets and fighting fires.

The only constant thing about our systems is that they change. If we define our systems as code, run them on dynamic infrastructure platforms, and deliver that code across our systems with a change pipeline, then we can make changes routine and easy. If our systems are only ever created and changed through code and pipelines, then we can ensure their consistency and be sure they align with whatever policies we need.

“What’s on a Server” and “Where Things Come From” describe what’s on a server and where it all comes from. Everything on a given server comes from a defined source, whether it’s an OS installation, system package repository, or server configuration code. Any change you need to make to a server is a change to one of these things.

This chapter is about how to change things on servers by changing the code that defines where the thing comes from and applying it one way or another. By implementing a reliable, automated change process for your servers, you ensure ...