[[settings]]
== Configuring Elasticsearch

Elasticsearch ships with good defaults and requires very little configuration.
Most settings can be changed on a running cluster using the
<<cluster-update-settings>> API.

The configuration files should contain settings which are node-specific (such
as `node.name` and paths), or settings which a node requires in order to be
able to join a cluster, such as `cluster.name` and `network.host`.

[float]
=== Config file location

Elasticsearch has two configuration files:

* `elasticsearch.yml` for configuring Elasticsearch, and
* `log4j2.properties` for configuring Elasticsearch logging.

These files are located in the config directory, whose location defaults to
`$ES_HOME/config/`.  The Debian and RPM packages set the config directory
location to `/etc/elasticsearch/`.

The location of the config directory can be changed with the `path.conf`
flag, as follows:

[source,sh]
-------------------------------
./bin/elasticsearch --path.conf /path/to/my/config/
-------------------------------

[float]
=== Config file format

The configuration format is http://www.yaml.org/[YAML]. Here is an
example of changing the path of the data and logs directories:

[source,yaml]
--------------------------------------------------
path:
    data: /var/lib/elasticsearch
    logs: /var/log/elasticsearch
--------------------------------------------------

Settings can also be flattened as follows:

[source,yaml]
--------------------------------------------------
path.data: /var/lib/elasticsearch
path.logs: /var/log/elasticsearch
--------------------------------------------------

[float]
=== Environment variable substitution

Environment variables referenced with the `${...}` notation within the
configuration file will be replaced with the value of the environment
variable, for instance:

[source,yaml]
--------------------------------------------------
node.name:    ${HOSTNAME}
network.host: ${ES_NETWORK_HOST}
--------------------------------------------------

[float]
=== Prompting for settings

For settings that you do not wish to store in the configuration file, you can
use the value `${prompt.text}` or `${prompt.secret}` and start Elasticsearch
in the foreground. `${prompt.secret}` has echoing disabled so that the value
entered will not be shown in your terminal; `${prompt.text}` will allow you to
see the value as you type it in. For example:

[source,yaml]
--------------------------------------------------
node:
  name: ${prompt.text}
--------------------------------------------------

When starting Elasticsearch, you will be prompted to enter the actual value
like so:

[source,sh]
--------------------------------------------------
Enter value for [node.name]:
--------------------------------------------------

NOTE: Elasticsearch will not start if `${prompt.text}` or `${prompt.secret}`
is used in the settings and the process is run as a service or in the background.