The index.lifecycle.name setting can be set in an index template so that it
is automatically applied to indexes matching the templates index pattern:
PUT _template/my_template
{
  "index_patterns": ["test-*"],  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 1,
    "index.lifecycle.name": "my_policy",
  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 1,
    "index.lifecycle.name": "my_policy",  "index.lifecycle.rollover_alias": "test-alias"
  }
}
    "index.lifecycle.rollover_alias": "test-alias"
  }
}| 
This template will be applied to all indexes which have a name starting
with  | |
| 
The template will set the policy to be used to  | 
Now that a policy exists and is used in an index template we can create an initial index which will be managed by our policy:
We can now write data to the test-alias alias. Because we have a rollover
action defined in our policy, when the index grows larger than 25GB index lifecycle management will
create a new index and roll the alias over to use the new index automatically.