Because base layer updates include operating system and other critical component updates, test a new base layer before distributing it to endpoints.
After you capture a base layer, select a sample group of endpoints and distribute the base layer to them to verify that no problems exist.
If the base layer is used with multiple hardware platforms, test one sample per platform. Also do a test distribution of a base layer to a typical user machine with user-installed applications to verify that the overall update results are satisfactory before you distribute to multiple endpoints.
The Base Layer Rules policy is used during first-time deployment to identify the parts of the endpoint that the base layer manages, and the parts to be left unmanaged at the endpoint. In an initial distribution, no previous base layer exists to compare against, so Mirage does not remove existing software from the endpoints before applying the base layer.