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lono cfn preview

Usage

lono cfn preview STACK

Description

Preview a CloudFormation stack update. This is similar to terraform’s plan or puppet’s dry-run mode.

Examples

We’ll make a change to the default InstanceType of a CloudFromation stack.

lono cfn preview my-stack

The output should look similiar to this:

Generating CloudFormation source code diff...
Running: colordiff /tmp/existing_cfn_template.yml output/templates/ec2.yml
14c14
<     Default: t2.small
---
>     Default: t2.micro
Generating CloudFormation Change Set for preview.....
CloudFormation preview for 'ec2' stack update. Changes:
Modify AWS::EC2::Instance: EC2Instance i-07e939db65120fb75

The preview includes colors:

Stack Update

There are two types of “diffs” in the preview.

  1. Source code diff of the templates. This is generated by downloading the current CloudFormation template and comparing it with the locally generated one using colordiff.
  2. CloudFormation Change Set list of changes. This is generated using AWS CloudFormation Change Set feature.

Options

    [--rollback], [--no-rollback]                    # rollback
                                                     # Default: true
    [--source=SOURCE]                                # url or path to file with template
    [--blueprint=BLUEPRINT]                          # override convention and specify the template file to use
    [--capabilities=one two three]                   # iam capabilities. Ex: CAPABILITY_IAM, CAPABILITY_NAMED_IAM
c, [--config=CONFIG]                                 # override convention and specify both the param and variable file to use
    [--iam], [--no-iam]                              # Shortcut for common IAM capabilities: CAPABILITY_IAM, CAPABILITY_NAMED_IAM
p, [--param=PARAM]                                   # override convention and specify the param file to use
    [--tags=key:value]                               # Tags for the stack. IE: Name:api-web Owner:bob
    [--template=TEMPLATE]                            # override convention and specify the template file to use
v, [--variable=VARIABLE]                             # override convention and specify the variable file to use
    [--change-set], [--no-change-set]                # Uses generated change set to update the stack.  If false, will perform normal update-stack.
                                                     # Default: true
    [--changeset-preview], [--no-changeset-preview]  # Show ChangeSet changes preview.
                                                     # Default: true
    [--codediff-preview], [--no-codediff-preview]    # Show codediff changes preview.
                                                     # Default: true
    [--param-preview], [--no-param-preview]          # Show parameter diff preview.
                                                     # Default: true
    [--keep], [--no-keep]                            # keep the changeset instead of deleting it afterwards
    [--verbose], [--no-verbose]                      
    [--noop], [--no-noop]

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