anchor.diff:  sudo sysctl -w vm.max_map_count=262144
   --------------------------------------------
   --
  +
   =========================
   
   The following example brings up a cluster comprising two {es} nodes.
  
positive.code: 
  . The image https://docs.docker.com/engine/reference/builder/#/expose[exposes]
  TCP ports 9200 and 9300. For clusters it is recommended to randomize the
  published ports with `--publish-all`, unless you are pinning one container per host.
  
  . Use the `ES_JAVA_OPTS` environment variable to set heap size. For example, to
  use 16GB, use `-e ES_JAVA_OPTS="-Xms16g -Xmx16g"` with `docker run`.
  
  . Pin your deployments to a specific version of the {es} Docker image, for
  example +docker.elastic.co/elasticsearch/elasticsearch:{version}+.
  
  . Always use a volume bound on `/usr/share/elasticsearch/data`, as shown in the
  <<docker-cli-run-prod-mode,production example>>, for the following reasons:
  
  .. The data of your {es} node won't be lost if the container is killed
  
  .. {es} is I/O sensitive and the Docker storage driver is not ideal for fast I/O
  
  .. It allows the use of advanced
  https://docs.docker.com/engine/extend/plugins/#volume-plugins[Docker volume plugins]
  
  . If you are using the devicemapper storage driver, make sure you are not using
  the default `loop-lvm` mode. Configure docker-engine to use
  https://docs.docker.com/engine/userguide/storagedriver/device-mapper-driver/#configure-docker-with-devicemapper[direct-lvm]
  instead.
  
  . Consider centralizing your logs by using a different
  https://docs.docker.com/engine/admin/logging/overview/[logging driver]. Also
  note that the default json-file logging driver is not ideally suited for
  production use.
  
  
  include::next-steps.asciidoc[]
  
negative.code: The images use https://hub.docker.com/_/centos/[centos:7] as the base image and
  are available with {xpack-ref}/xpack-introduction.html[X-Pack].
  
  A list of all published Docker images and tags can be found in https://www.docker.elastic.co[www.docker.elastic.co]. The source code can be found
  on https://github.com/elastic/elasticsearch-docker/tree/{branch}[GitHub].
  
  ==== Image types
  