App Variables are values that you can store in the API to be used across all installs of an app.

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Defining App Variables

You can create App Variables using the CLI. 
nuon apps variables create --name=external_api_key --value=b25yYW5nZXRpZ2h0bHlhdHRlbXB0cGxlbnR5cmVhZGRvdWJsZXdlc3RleWVodW50d2g=
Once created you should be able to view the default using the CLI. 
nuon apps variables list
If you no longer need the default, you can delete it using the CLI 
nuon variables delete --id=apsmsj5rucsdc758c2cs6x7geu

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Using App Variables

App Variables are included in the install state, and are available in job plans. Using our example secret named external_api_key, you could interpolate it’s value in your app config using {{ .nuon.app.variables.external_api_key }}.
If you add or a update an app default after an install has been created. You will need to update that install’s state before the value will be included in plans. Running a deploy or sandbox provision will trigger a state update.