Collectively, we have a lot of experience with users suffering unexpected issues because they have not configured important settings. In previous versions of Elasticsearch, misconfiguration of some of these settings were logged as warnings. Understandably, users sometimes miss these log messages. To ensure that these settings receive the attention that they deserve, Elasticsearch has bootstrap checks upon startup.

These bootstrap checks inspect a variety of Elasticsearch and system settings and compare them to values that are safe for the operation of Elasticsearch. If Elasticsearch is in development mode, any bootstrap checks that fail appear as warnings in the Elasticsearch log. If Elasticsearch is in production mode, any bootstrap checks that fail will cause Elasticsearch to refuse to start.

There are some bootstrap checks that are always enforced to prevent Elasticsearch from running with incompatible settings. These checks are documented individually.

Development vs. production modeedit

By default, Elasticsearch binds to localhost for HTTP and transport (internal) communication. This is fine for downloading and playing with Elasticsearch, and everyday development but it’s useless for production systems. To form a cluster, Elasticsearch instances must be reachable via transport communication so they must bind transport to an external interface. Thus, we consider an Elasticsearch instance to be in development mode if it does not bind transport to an external interface (the default), and is otherwise in production mode if it does bind transport to an external interface. Note that HTTP can be configured independently of transport via http.host and transport.host; this can be useful for configuring a single instance to be reachable via HTTP for testing purposes without triggering production mode.