Update the Stack
Now is a good time to introduce
lono cfn update command before moving on. In the previous section, we used the
lono cfn create command and assumed that the template magically worked the very first time. In practice, it usually takes a few iterations before you get the CloudFormation template working right. The CloudFormation development flow more commonly goes:
Let’s make a simple change to test out the
lono cfn update command. We’ll change the default InstanceType from
t2.micro and then run:
lono cfn update ec2
The output should look similiar to this:
Notice that before the update gets performed lono provides a preview of the changes that are about to take place. There are two types of “diffs” in the preview.
- Source code diff of the templates. This is generated by downloading the current CloudFormation template and comparing it with the locally generated one using
- CloudFormation Change Set list of changes. This is generated using AWS CloudFormation Change Set feature.
You are prompted with an “Are you sure?” confirmation before lono continues.
By default, the update command will display a preview of the stack changes before applying the update and prompt to check if you are sure. If you want to bypass the are you sure prompt, use the
lono cfn update ec2 --sure
You’ll find the
lono cfn update command helpful in the sections.
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