Disable replicas of an existing index in Elasticsearch

To disable replicas of an existing index in Elasticsearch, do as follows:

curl -XPUT 'localhost:9200/logstash-2016.07.18/_settings' -d '
{
  "index" : {
    "number_of_replicas" : 0
  }
}'

Reference:
https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-update-settings.html