How to add a node to an Elasticsearch cluster

Adding a node to an Elasticsearch cluster increases indexing and search capacity, spreads shard copies across more hosts, and reduces the impact of maintenance or hardware loss on any single node.

In self-managed Elasticsearch, a new node joins over the transport layer after it can discover the cluster's master-eligible peers and match the existing cluster identity. Current package installs commonly enable TLS and authentication automatically, so adding a node often starts with a short-lived enrollment token that writes the security and discovery settings needed for the first join.

The join succeeds only when the new node uses the same cluster.name, can reach the existing master-eligible nodes on port 9300, and does not carry leftover bootstrap settings from a brand-new cluster. On DEB and RPM installs, run elasticsearch-reconfigure-node before the new node starts for the first time. On archive or manually configured installs, set the equivalent security and discovery values directly in /etc/elasticsearch/elasticsearch.yml. After the second node is added, keep discovery.seed_hosts current on every node and remove cluster.initial_master_nodes so later restarts rejoin cleanly.

Steps to add a node to an Elasticsearch cluster:

List the current cluster nodes on an existing node and note the master-eligible transport endpoints that the new node must reach.
```
$ curl -sS -u "elastic:$ELASTIC_PASSWORD" "https://node-01:9200/_cat/nodes?v&h=ip,name,node.role,master"
ip         name     node.role   master
192.0.2.40 node-01  cdfhilmrstw *
192.0.2.41 node-02  cdfhilmrstw -
```
Use the HTTP endpoint that already works for the cluster. The master marker must show exactly one *, and the new node must be able to reach the master-eligible peers over transport on port 9300.
Generate a node enrollment token on any existing secured node in the cluster.
```
$ sudo /usr/share/elasticsearch/bin/elasticsearch-create-enrollment-token -s node
```
The token expires after about 30 minutes. Create a fresh token for each new node.
Reconfigure the new package-installed node with the enrollment token before starting Elasticsearch on that host for the first time.
```
$ sudo /usr/share/elasticsearch/bin/elasticsearch-reconfigure-node --enrollment-token &lt;node-enrollment-token&gt;
```
This step applies to DEB and RPM installs with security enabled. Archive, tarball, and other manually configured deployments do not use elasticsearch-reconfigure-node and must set the equivalent TLS and discovery settings directly.
Open /etc/elasticsearch/elasticsearch.yml on the new node.
```
$ sudoedit /etc/elasticsearch/elasticsearch.yml
```
Set the shared cluster name, a unique node name, and a routable network address on the new node.
```
cluster.name: search-cluster
node.name: node-03
network.host: 192.0.2.42
```
cluster.name must match the existing cluster exactly. Use a fixed address for network.host so the node can publish a reachable HTTP and transport address.
Ensure discovery.seed_hosts contains the transport addresses of the current master-eligible nodes.
```
discovery.seed_hosts:
  - 192.0.2.40:9300
  - 192.0.2.41:9300
```
On package installs, elasticsearch-reconfigure-node usually writes this setting already. Review it instead of assuming it is complete, especially after the cluster grows beyond two nodes.

Related: How to set Elasticsearch discovery seed hosts
Remove cluster.initial_master_nodes from the new node if it is present.
```
cluster.initial_master_nodes:
  - node-01
  - node-02
```
cluster.initial_master_nodes is only for the first bootstrap of a brand-new cluster. Leaving it in place on a joining or restarting node can trigger discovery bootstrap failures or an unintended new cluster.
Review node.roles only if the new host is meant to be dedicated to specific work.

Leaving node.roles unset keeps the default role set. Setting node.roles explicitly replaces that default, so include every role the new node is supposed to provide.

Related: How to configure Elasticsearch node roles
Enable and start the elasticsearch service on the new node.
```
$ sudo systemctl enable --now elasticsearch
```
The first start can take time while the node applies its security material and joins the existing cluster state.

Related: How to manage the Elasticsearch service with systemctl in Linux
Update the existing nodes so every master-eligible node has the current discovery.seed_hosts list and no cluster.initial_master_nodes setting.

The first installed node in a multi-node package deployment also needs a complete seed-host list, or later restarts can fail discovery bootstrap checks even after the new node joined successfully.

Related: How to set Elasticsearch discovery seed hosts

Verify that the new node appears in the cluster node list.

$ curl -sS -u "elastic:$ELASTIC_PASSWORD" "https://node-01:9200/_cat/nodes?v&h=ip,name,node.role,master"
ip         name     node.role   master
192.0.2.40 node-01  cdfhilmrstw *
192.0.2.41 node-02  cdfhilmrstw -
192.0.2.42 node-03  cdfhilmrstw -

The compact node.role string reflects the roles currently assigned to each node. If the new node is missing, recheck transport reachability, cluster.name, TLS trust, and the seed-host list.

Check cluster health after the new node joins.

$ curl -sS -u "elastic:$ELASTIC_PASSWORD" "https://node-01:9200/_cluster/health?pretty&filter_path=cluster_name,status,timed_out,number_of_nodes,number_of_data_nodes,relocating_shards,initializing_shards,unassigned_shards,active_shards_percent_as_number"
{
  "cluster_name" : "search-cluster",
  "status" : "green",
  "timed_out" : false,
  "number_of_nodes" : 3,
  "number_of_data_nodes" : 3,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 0,
  "active_shards_percent_as_number" : 100.0
}

status can stay yellow briefly while replica shards relocate to the new node. Use the node count, relocation counters, and unassigned-shard count to confirm the join completed cleanly.