/etc/security/limits.conf:
elasticsearch - nofile 65535
elasticsearch - memlock unlimited

/etc/default/elasticsearch:
ES_HEAP_SIZE=512m
MAX_OPEN_FILES=65535
MAX_LOCKED_MEMORY=unlimited

/etc/elasticsearch/elasticsearch.yml:
bootstrap.mlockall: true


References:
https://github.com/grigorescu/Brownian/wiki/ElasticSearch-Configuration
http://www.elasticsearch.org/guide/reference/setup/installation/


grandparent/parent/child example:
https://gist.github.com/ToulBoy/1941432