.. _config_overview_bootstrap: Bootstrap configuration ----------------------- To use the xDS API, it's necessary to supply a bootstrap configuration file. This provides static server configuration and configures Envoy to access :ref:`dynamic configuration if needed `. This is supplied on the command-line via the :option:`-c` flag, i.e.: .. code-block:: console ./envoy -c .{json,yaml,pb,pb_text} where the extension reflects the underlying config representation. The :ref:`Bootstrap ` message is the root of the configuration. A key concept in the :ref:`Bootstrap ` message is the distinction between static and dynamic resources. Resources such as a :ref:`Listener ` or :ref:`Cluster ` may be supplied either statically in :ref:`static_resources ` or have an xDS service such as :ref:`LDS ` or :ref:`CDS ` configured in :ref:`dynamic_resources `.