Updating a Heat stack

Our running Stack is based on templates, so this allows us to modify our application stack by altering the inputs. If we wanted to change the size of a flavor, or the key used, you can trigger a rebuild of the instances in the stack by altering the inputs and issuing the stack update command.

Getting ready

Ensure that you are logged on to a correctly configured OpenStack client and can access the OpenStack environment. Refer to Chapter 2, The OpenStack Client, for details of setting up your environment to use OpenStack.

How to do it...

In this section, we'll modify the environment file to change a flavor from m1.tiny to m1.large. (Ensure that you have a valid flavor with this name before continuing!)

1. We first edit the environment file, called cookbook-env.yaml, to show the changes we want to make to our running stack:

   parameters:
     key_name: demokey
     image: xenial-image
     flavor: m1.large
     public_net_id: 2da8979e-dcf8-4eb8-b207-f33bfce4a15a
     private_net_id: 78a5a119-c27a...