1. Learn Pulumi
  2. Building with Pulumi
  3. Understanding Stacks

Understanding Stacks

Every Pulumi program is deployed to a stack. A stack is an isolated, independently configurable instance of a Pulumi program. Stacks are commonly used to denote different phases of development (such as development, staging, and production) or feature branches (such as feature-x-dev).

A project can have as many stacks as you need. By default, Pulumi creates a stack for you when you start a new project using the pulumi new command.

Create a stack

To create a new stack, we use the command pulumi stack init name. This command creates an empty stack name and sets it as the active stack. The project that the stack is associated with is determined by finding the nearest Pulumi.yaml file.

The stack name must be unique within a project. Stack names may only contain alphanumeric characters, hyphens, underscores, or periods.

Let’s create a new stack in our project, for our staging environment:

$ pulumi stack init staging

Listing stacks

We have a couple of stacks in our project now—but how do we know which ones we have? If we run the command pulumi stack ls, it will tell us!

$ pulumi stack ls
dev       2 minutes ago  10              https://app.pulumi.com/***/my-first-app/dev
staging*  n/a            n/a             https://app.pulumi.com/***/my-first-app/staging

Notice that the staging stack has an * after its name; this asterisk marks this stack as the active stack (i.e., the stack that all our commands will run on).

Selecting stacks

When we run a Pulumi command (such as config, up, or destroy), the command operates on the active stack. But what if we want to change which stack is active? For this task, we use the pulumi stack select command:

$ pulumi stack select dev

$ pulumi stack ls
dev*     3 minutes ago  10              https://app.pulumi.com/***/my-first-app/dev
staging  n/a            n/a             https://app.pulumi.com/***/my-first-app/staging

Notice that dev is now the active stack.

Next up, we’re going to explore how to get information out of a stack to use in other places, like elsewhere in our program or in general spots like your browser.