There is a manual https://www.elastic.co/guide/en/elasticsearch/reference/current/setup-upgrade.html
with some Disable shard allocation, Stop non-essential indexing, Shut down a single node... blah, blah, blah.
But where is the software info? How to rewrite existing copy with the new version? This manual says noting about software installation
I just copied 'data' directory to new installation. Looks like this is the way.