[role="xpack"]
[testenv="basic"]
[[encrypting-communications-hosts]]
=== Add nodes to your cluster

You can add more nodes to your cluster and optionally designate specific
purposes for each node. For example, you can allocate master nodes, data nodes,
ingest nodes, machine learning nodes, and dedicated coordinating nodes. For
details about each node type, see {ref}/modules-node.html[Nodes].

Let's add two nodes to our cluster!

. Install two additional copies of {es}. It's possible to run multiple {es}
nodes using a shared installation. In this tutorial, however, we're keeping
things simple by using the `zip` or `tar.gz` packages and by putting each copy
in a separate folder. You can simply repeat the steps that you used to install
{es} in the 
{stack-gs}/get-started-elastic-stack.html#install-elasticsearch[Getting started with the {stack}]
tutorial.

. Generate certificates for the two new nodes.
+
--
For example, run the following command:

["source","sh",subs="attributes,callouts"]
----------------------------------------------------------------------
./bin/elasticsearch-certutil cert \
--ca elastic-stack-ca.p12 \ <1>
--multiple
----------------------------------------------------------------------
<1> Use the certificate authority that you created in <<encrypting-communications-certificates>>.

You are prompted for information about each new node. Specify `node-2` and
`node-3` for the instance names. For the purposes of this tutorial, specify the
same IP address (`127.0.0.1,::1`) and DNS name (`localhost`) for each node.

You are prompted to enter the password for your CA. You are also prompted to
create a password for each certificate.

By default, the command produces a zip file named `certificate-bundle.zip`,
which contains the generated certificates and keys.
--

. Decompress the `certificate-bundle.zip` file. For example:
+
--
["source","sh",subs="attributes,callouts"]
----------------------------------------------------------------------
unzip certificate-bundle.zip 

Archive:  certificate-bundle.zip
   creating: node-2/
  inflating: node-2/node-2.p12       
   creating: node-3/
  inflating: node-3/node-3.p12   
----------------------------------------------------------------------
  
The `certificate-bundle.zip` file contains a folder for each of your nodes. Each
folder contains a single PKCS#12 keystore that includes a node certificate,
node key, and CA certificate.
--

. Create a folder to contain certificates in the configuration directory of each
{es} node. For example, create a `certs` folder in the `config` directory.

. Copy the appropriate certificate to the configuration directory on each node.
For example, copy the `node-2.p12` file into the `config/certs` directory on the
second node and the `node-3.p12` into the `config/certs` directory on the third
node.

. Specify the name of the cluster and give each node a unique name.
+
--
For example, add the following settings to the `ES_PATH_CONF/elasticsearch.yml`
file on the second node:

[source,yaml]
----
cluster.name: test-cluster
node.name: node-2
----

Add the following settings to the `ES_PATH_CONF/elasticsearch.yml`
file on the third node:

[source,yaml]
----
cluster.name: test-cluster
node.name: node-3
----

NOTE: In order to join the same cluster as the first node, they must share the
same `cluster.name` value.

--

. (Optional) Provide seed addresses to help your nodes discover other nodes with
which to form a cluster.
+
--
For example, add the following setting in the `ES_PATH_CONF/elasticsearch.yml`
file:

[source,yaml]
----
discovery.seed_hosts: ["localhost"]
----

The default value for this setting is `127.0.0.1, [::1]`, therefore it isn't
actually required in this tutorial. When you want to form a cluster with nodes
on other hosts, however, you must use this setting to provide a list of
master-eligible nodes to seed the discovery process. For more information, see
{ref}/modules-discovery-hosts-providers.html[Discovery].
--

. On each node, enable TLS for transport communications. You must also configure
each node to identify itself using its signed certificate.
+
--
include::tutorial-tls-internode.asciidoc[tag=enable-tls]
--

. On each node, store the password for the PKCS#12 file in the {es} keystore.
+
--
include::tutorial-tls-internode.asciidoc[tag=secure-passwords]

On the second node, supply the password that you created for the `node-2.p12`
file. On the third node, supply the password that you created for the
`node-3.p12` file.
--

. Start each {es} node. For example, if you installed {es} with a `.tar.gz`
package, run the following command from each {es} directory:
+
--
["source","sh",subs="attributes,callouts"]
----------------------------------------------------------------------
./bin/elasticsearch
----------------------------------------------------------------------

See {ref}/starting-elasticsearch.html[Starting {es}].

If you encounter errors, you can see some common problems and solutions in
<<trb-security-ssl>>.
--

. Verify that your cluster now contains three nodes.
+
--
For example, log into {kib} with the `elastic` built-in user. Go to
*Dev Tools > Console* and run the {ref}/cluster-health.html[cluster health API]:

[source,console]
----------------------------------
GET _cluster/health
----------------------------------

Confirm the `number_of_nodes` in the response from this API.

You can also use the {ref}/cat-nodes.html[cat nodes API] to identify the master
node:

[source,console]
----------------------------------
GET _cat/nodes?v
----------------------------------

The node that has an asterisk(*) in the `master` column is the elected master
node. 
--

Now that you have multiple nodes, your data can be distributed across the
cluster in multiple primary and replica shards. For more information about the
concepts of clusters, nodes, and shards, see
{ref}/getting-started.html[Getting started with {es}].

[discrete]
[[encrypting-internode-nextsteps]]
=== What's next?

Congratulations! You've encrypted communications between the nodes in your
cluster and can pass the 
{ref}/bootstrap-checks-xpack.html#bootstrap-checks-tls[TLS bootstrap check].

If you want to encrypt communications between other products in the {stack}, see
<<encrypting-communications>>.
