红帽全球峰会3.4. 示例 4：启用和禁用参数
在某些情况下，您可能需要首先在部署期间设置参数，然后为将来的部署操作禁用 参数，如更新或扩展操作。例如，要在 overcloud 创建过程中包括自定义 RPM，您需要包括以下内容：
parameter_defaults: DeployArtifactURLs: ["http://www.example.com/myfile.rpm"]
parameter_defaults:
DeployArtifactURLs: ["http://www.example.com/myfile.rpm"]如果您需要从将来的部署中禁用这个参数，则它不足以移除该参数。相反，您要将参数设置为空值：
parameter_defaults: DeployArtifactURLs: []
parameter_defaults:
DeployArtifactURLs: []这样可确保不再为后续部署操作设置该参数。
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