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Check mode is a feature of Ansible that allows playbooks to be run without making any changes. Modules that support check mode report the changes they would have made. Modules that do not support check mode are skipped when the playbook is run with --check.
The Ansible collection for PowerMax 1.6 introduced check mode for all control modules. Check mode is a way of running a playbook with the reassurance that no changes will be made, but you can check if any changes occurred.
Check mode is a simulation. It does not generate output for tasks that use conditionals based on registered variables (results of prior tasks). However, check mode is useful for validating configuration management playbooks that run on one node at a time. To run a playbook in check mode, run your playbook with the optional --check.
Figure 43 shows a playbook run with check mode. The playbook contents have been modified to set the service level on the storage group to Diamond, but the referenced storage group has the service level set to Bronze. Running the playbook with check mode shows that the first task in the playbook would make a change.
Checking the current state of the storage group in Unisphere shows that the playbook run with check mode did indeed make no changes.
The check mode functionality is useful should you want to introduce change control and Continuous Integration and Continuous Delivery (CI/CD) workflows to manage your infrastructure as code. Before implementing changes, you can use the last known state from version control and run the playbook with check mode to ensure that the environment is in the expected state. You can also run the newer version of the playbook with check mode to verify the tasks that will make changes and that the number of changes matches with change control before implementing the changes.