elasticsearch/docs/reference/setup/important-settings/cluster-name.asciidoc

[[cluster.name]]
=== `cluster.name`

A node can only join a cluster when it shares its `cluster.name` with all the
other nodes in the cluster. The default name is `elasticsearch`, but you should
change it to an appropriate name which describes the purpose of the cluster.

[source,yaml]
--------------------------------------------------
cluster.name: logging-prod
--------------------------------------------------

Make sure that you don't reuse the same cluster names in different environments,
otherwise you might end up with nodes joining the wrong cluster.