After upgrading to Elasticsearch 2.0 (running on Debian 8 “Jessie”), I noticed it didn’t start automatically anymore. A service elasticsearch status returned this:
● elasticsearch.service - Elasticsearch Loaded: loaded (/usr/lib/systemd/system/elasticsearch.service; disabled) Active: active (running) since Fri 2015-10-30 23:27:04 CET; 23min ago
Notice the disabled part? You need to manually enable it again.