Check the health of an Elasticsearch cluster

curl -s 'localhost:9200/_cluster/health?pretty'

# one line per index — yellow is almost always unassigned replicas
curl -s 'localhost:9200/_cat/indices?v&h=health,index,docs.count,store.size'

# and which shards were never assigned
curl -s 'localhost:9200/_cat/shards?v' | grep UNASSIGNED