Still getting the same Kibana error "Your Kibana index is out of date, reset it or use the X-Pack upgrade assistant", even after deleting the .kibana index and restarting the Kibana process
Ref: https://www.elastic.co/guide/en/kibana/6.0/migrating-6.0-index.html
{
  "name": "localhost",
  "uuid": "304303b5-5f61-4770-b038-8416b04fc401",
  "version": {
    "number": "6.0.1",
    "build_hash": "8e27db38d19e7246b985612db0a07837ff4ea6b9",
    "build_number": 16108,
    "build_snapshot": false
  },
  "status": {
    "overall": {
      "state": "red",
      "title": "Red",
      "nickname": "Danger Will Robinson! Danger!",
      "icon": "danger",
      "since": "2019-04-24T18:43:19.164Z"
    },
    "statuses": [
      {
        "id": "plugin:elasticsearch@6.0.1",
        "state": "red",
        "icon": "danger",
        "message": "Your Kibana index is out of date, reset it or use the X-Pack upgrade assistant.",
        "since": "2019-04-24T18:43:19.164Z"
      }
    ]
  }
}
===========================================
curl localhost:9200
{
  "name" : "md6KhUj",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "3FOSEhn7TMa6aHgIPfK0kA",
  "version" : {
    "number" : "6.0.1",
    "build_hash" : "d951bbf",
    "build_date" : "2017-12-07T01:43:54.348Z",
    "build_snapshot" : false,
    "lucene_version" : "7.0.1",
    "minimum_wire_compatibility_version" : "5.6.0",
    "minimum_index_compatibility_version" : "5.0.0"
  },
  "tagline" : "You Know, for Search"
}