Hey. I wanted to upgrade elasticsearch from 7.16 to 8.7. First I upgraded ES to 7.17 but I didn't restarted the service and immediately upgraded to 8.7. Now Elasticsearch wont start due to error:
cannot upgrade a node from version [7.16.2] directly to version [8.7.1], upgrade to version [7.17.0] first.
I have backed up configuration directory, /etc/elasticsearch and data directory where we store indices.
When you have upgraded to 7.17 you must restart the service and run the migration assistant in order to identify any issues you need to fix before upgrading further. As far as I recall this is described in the documentation.