Allows to update cluster wide specific settings. Settings updated can either be persistent (applied cross restarts) or transient (will not survive a full cluster restart). Here is an example:

curl -XPUT localhost:9200/_cluster/settings -d '{
    "persistent" : {
        "discovery.zen.minimum_master_nodes" : 2
    }
}'

Or:

curl -XPUT localhost:9200/_cluster/settings -d '{
    "transient" : {
        "discovery.zen.minimum_master_nodes" : 2
    }
}'

The cluster responds with the settings updated. So the response for the last example will be:

{
    "persistent" : {},
    "transient" : {
        "discovery.zen.minimum_master_nodes" : "2"
    }
}'

Cluster wide settings can be returned using:

curl -XGET localhost:9200/_cluster/settings

A list of dynamically updatable settings can be found in the Modules documentation.