Most OpenSearch configuration can take place in the cluster settings API. Certain operations require you to modify `opensearch.yml` and restart the cluster.
Whenever possible, use the cluster settings API instead; `opensearch.yml` is local to each node, whereas the API applies the setting to all nodes in the cluster.
## Cluster settings API
The first step in changing a setting is to view the current settings:
```
GET _cluster/settings?include_defaults=true
```
For a more concise summary of non-default settings:
```
GET _cluster/settings
```
Three categories of setting exist in the cluster settings API: persistent, transient, and default. Persistent settings, well, persist after a cluster restart. After a restart, OpenSearch clears transient settings.
If you specify the same setting in multiple places, OpenSearch uses the following precedence:
1. Transient settings
2. Persistent settings
3. Settings from `opensearch.yml`
4. Default settings
To change a setting, just specify the new one as either persistent or transient. This example shows the flat settings form:
```json
PUT /_cluster/settings
{
"persistent" : {
"action.auto_create_index" : false
}
}
```
You can also use the expanded form, which lets you copy and paste from the GET response and change existing values:
```json
PUT /_cluster/settings
{
"persistent": {
"action": {
"auto_create_index": false
}
}
}
```
---
## Configuration file
You can find `opensearch.yml` in `/usr/share/opensearch/config/opensearch.yml` (Docker) or `/etc/opensearch/opensearch.yml` (RPM and DEB) on each node.
The demo configuration includes a number of settings for the security plugin that you should modify before using OpenSearch for a production workload. To learn more, see [Security]({{site.url}}{{site.baseurl}}/security-plugin/).
