Yellow means the primary data shards are assigned but at least one replica copy has no assigned node. Red means at least one primary has no assigned node, so some data may be unavailable.
Identify the affected shard
In Kibana Dev Tools, start with:
GET /_cat/shards?v&h=index,shard,prirep,state,node
An illustrative row means replica of shard 0 has no destination. If , the primary, is unassigned instead, investigate data availability urgently.
