Add docs for stopping Elasticsearch

This commit adds docs for the Elasticsearch shutdown process,
distinguishing between a clean shutdown and an unclean halt due to fatal
error.

Author: jasontedor

docs/reference/setup.asciidoc

@@ -47,3 +47,5 @@ include::setup/bootstrap-checks.asciidoc[]
 include::setup/sysconfig.asciidoc[]
 
 include::setup/upgrade.asciidoc[]
+
+include::setup/stopping.asciidoc[]

docs/reference/setup/stopping.asciidoc

@@ -0,0 +1,44 @@
+[[stopping-elasticsearch]]
+=== Stopping Elasticsearch
+
+An orderly shutdown of Elasticsearch ensures that Elasticsearch has a chance to cleanup and close
+outstanding resources. For example, a node that is shutdown in an orderly fashion will remove itself
+from the cluster, sync translogs to disk, and perform other related cleanup activities. You can help
+ensure an orderly shutdown by properly stopping Elasticsearch.
+
+If you're running Elasticsearch as a service, you can stop Elasticsearch via the service management
+functionality provided by your installation.
+
+If you're running Elasticsearch directly, you can stop Elasticsearch by sending control-C if you're
+running Elasticsearch in the console, or by sending `SIGTERM` to the Elasticsearch process on a
+POSIX system. You can obtain the PID to send the signal to via various tools (e.g., `ps` or `jps`)
+or by specifying a location to write a PID file to on startup (`-p <path>`).
+
+[source,sh]
+--------------------------------------------------
+$ ./bin/elasticsearch -p /tmp/elasticsearch-pid -d
+$ cat /tmp/elasticsearch-pid && echo
+7801
+$ kill -SIGTERM 7801
+--------------------------------------------------
+
+[[fatal-errors]
+[float]
+=== Stopping on Fatal Errors
+
+During the life of the Elasticsearch virtual machine, certain fatal errors could arise that put the
+virtual machine in a questionable state. Such fatal errors include out of memory errors, internal
+errors in virtual machine, and serious I/O errors.
+
+When Elasticsearch detects that the virtual machine has encountered such a fatal error Elasticsearch
+will attempt to log the error and then will halt the virtual machine. When Elasticsearch initiates
+such a shutdown, it does not go through an orderly shutdown as described above. The Elasticsearch
+process will also return with a special status code indicating the nature of the error.
+
+[horizontal]
+JVM internal error:: 128
+Out of memory error:: 127
+Stack overflow error:: 126
+Unknown virtual machine error:: 125
+Serious I/O error:: 124
+Unknown fatal error:: 1