A private service account key file in JSON format. Instead of a key file <ahref="https://developers.google.com/identity/protocols/application-default-credentials">Google Application Default Credentials</a> can be used.
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<code>rootdirectory</code>
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no
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This is a prefix that will be applied to all Google Cloud Storage keys to allow you to segment data in your bucket if necessary.
`bucket`: The name of your Google Cloud Storage bucket where you wish to store objects (needs to already be created prior to driver initialization).
`keyfile`: (optional) A private key file in JSON format, used for [Service Account Authentication](https://cloud.google.com/storage/docs/authentication#service_accounts).
**Note** Instead of a key file you can use [Google Application Default Credentials](https://developers.google.com/identity/protocols/application-default-credentials).
`rootdirectory`: (optional) The root directory tree in which all registry files will be stored. Defaults to the empty string (bucket root).