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The build instance must be a docker Docker host to use this feature, and the the dockerBuildProjectImage operation of the FlexDeployDockerPluginmust must be associated to the build instance. See Creating and Editing Instances for more information on how to add a plugin operation to an Instance.
Optionally, a path to Dockerfile can be provided. If it is empty, a default Dockerfile will be used from Dockerfile in a project source checkout folder is expected. If the checkout folder is empty, then a Dockerfile is expected in the root of the source folderFD_TEMP_DIR. A Dockerfile must be present to build an image. This behavior changed slightly in 5.0.3 beta. Previously, the location was expected to be in FD_TEMP_DIR/FD_PROJECT_NAME.