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Starting a product on a preferred profile starts only a subset of features bundled in the product. In order to identify what feature bundles apply to which profile, each product maintains a set of bundles.info files in the <PRODUCT_HOME>/repository/components/<profile-name>/configuration/org.eclipse.equinox.simpleconfigurator directories. The bundles.info files contain references to the actual bundles. Note that <profile-name> in the directory path refers to the name of the profile. For example, when there's a product profile named webapp, references to all the feature bundles required for the webapp profile to function are in a bundles.info file saved in the <PRODUCT_HOME>/repository/components/webapp/configuration/org.eclipse.equinox.simpleconfigurator directory.
Note that when you start the server without using a preferred profile, the server refers to the <PRODUCT_HOME>/repository/components/default/configuration/org.eclipse.equinox.simpleconfigurator/bundles.info file by default. This file contains references to all bundles in the <PRODUCT_HOME>/repository/components/plugins directory, which is where all components/bundles of a product are saved.