Terraform Modules

What this chapter covers

Modules package Terraform configuration so you can reuse it. This chapter covers where module code comes from, how values move between a module and its caller, and how you call and version modules safely.

It has two parts: module sources and variable scope, then calling modules in configuration and managing their versions with constraints and terraform init.

Questions are single-answer, multiple-answer ("Pick the 2 correct responses below") and true or false statements, mostly direct recall of commands and behavior plus short HCL snippets that open "Consider the following configuration snippet:". There are no exhibits.

How the topics fit together

The source argument says where the module lives and terraform init installs it. The caller then passes values in through input variables and reads results back through outputs, while the version constraint controls which release is used.

• Source questions ask which source string is valid for a local path, registry, Git or bucket.
• Scope questions ask how a child gets a value and how the parent reads one back.
• Usage questions show a module block and ask what each argument does.
• Version questions ask what a constraint allows and which sources accept version.

How to use these pages

Each topic page has the same shape, so you can skim for what you need.

• What it is: the idea in plain words.
• How it works: the mechanism, with tables and examples.
• What to remember for the exam: the facts to memorize and how questions are phrased.
• Common mistakes: the classic traps.
• Check yourself: three questions to test your understanding.