Elasticsearch 503 error when checking server status

There could be another instance in your local network with elasticsearch server up and running. Since shards in elasticsearch are working from the box and enabled by default there could be a conflict of master node. Please review your elasticsearch.log file. If there is something like

{"error":"MasterNotDiscoveredException[waited for [30s]]","status":503} 

You should go to your config file /etc/elasticsearch/elasticsearch.yml and add this line:

discovery.zen.ping.multicast.enabled: false

in addition check value of

discovery.zen.ping.unicast.hosts

because it is necessary to discover elastic nodes