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using-templates.md

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Using templates

PSRule for Azure discovers and analyzes Azure resources contained within template and parameter files. To enable this feature, you need to:

  • Enable expansion.
  • Link parameter files to templates.

!!! Abstract This topic covers how you can validate Azure resources within template .json files. To learn more about why this is important see Expanding source files.

Enabling expansion

To expand parameter files configure ps-rule.yaml with the AZURE_PARAMETER_FILE_EXPANSION option.

# YAML: Enable expansion for template expansion.
configuration:
  AZURE_PARAMETER_FILE_EXPANSION: true

Linking templates

PSRule for Azure automatically detects parameter files and uses the following logic to link templates or Bicep modules.

  • By metadata — Check parameter file for a metadata link identifying the associated template.
  • By naming convention — Check for matching template files using file naming convention.

!!! Note Metadata links take priority over naming convention. For details on both options continue reading.

!!! Tip Linking templates also applies to Bicep modules when you are using .json parameter files.

By metadata

A parameter file can be linked to an associated template or Bicep module by setting metadata. To link a template within a parameter file, set the metadata.template property to the path of the template.

PSRule for Azure supports either:

  • Relative to repository — By default, the path is relative to the root of the repository.
  • Relative to template — To use a path relative to the parameter file, prefix the path with ./.

!!! Tip Referencing a path outside of the repository is blocked as this could lead to unintended exposure.

=== "Relative to repository"

The following example shows linking to a template which is stored within a hierarchical `template/` sub-directory.

!!! Example

    ```json
    {
        "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentParameters.json#",
        "contentVersion": "1.0.0.0",
        "metadata": {
            "template": "templates/storage/v1/template.json"
        },
        "parameters": {
        }
    }
    ```

=== "Relative to parameter file"

The following example shows linking to a template that is in the same directory as the parameter file.

!!! Example

    ```json
    {
        "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentParameters.json#",
        "contentVersion": "1.0.0.0",
        "metadata": {
            "template": "./storage.template.json"
        },
        "parameters": {
        }
    }
    ```

Additional benefits you get by using metadata links include:

  • You can share a common set of versioned templates across multiple deployments in a repository. This works great to mono-repositories.
  • You can discover all the deployments using a specific template by reading metadata. PSRule for Azure includes the Get-AzRuleTemplateLink cmdlet to list parameter file links.

!!! Tip By default, metadata links are not required. By configuring the AZURE_PARAMETER_FILE_METADATA_LINK option to true, this can be enforced. When configured, PSRule for Azure will fail parameter files that do not contain a metadata link. For details on AZURE_PARAMETER_FILE_METADATA_LINK see Configuring expansion.

!!! Note Bicep modules can also be expanded from parameter files. Instead of specifying a template path, you can specify the path to a Bicep file.

!!! Note You may find while editing a .json parameter file the root metadata property is flagged with a warning. For example Property metadata is not allowed.. This doesn't affect the workings of the parameter file or deployment. If you like a detailed description continue reading Troubleshooting.

By naming convention

When metadata links are not set, PSRule will fallback to use a naming convention to link to template files.

!!! Example A parameter file named azuredeploy.parameters.json links to the template file named azuredeploy.json.

PSRule for Azure supports linking by naming convention when:

  • Parameter files end with .parameters.json linking to ARM templates or Bicep modules.
  • The parameter file prefix matches the file name of the template or Bicep module. For example, azuredeploy.parameters.json links to azuredeploy.json or azuredeploy.bicep.
  • If both an ARM template and Bicep module exist, the template (.json) is preferred. For example, azuredeploy.parameters.json chooses azuredeploy.json over azuredeploy.bicep if both exist.
  • Both parameter file and template or Bicep module must be in the same directory.

The following is not currently supported:

  • Using a different naming convention for parameter files such as <templateName>.param.json.
  • Template or parameter files with alternative file extensions such as .jsonc.

*[WAF]: Well-Architected Framework *[ARM]: Azure Resource Manager *[CI]: continuous integration *[PR]: Pull Request