We just have one index in this cluster. The number of shards has always been 8. (Now, I wonder how they set it up so it could produce 8 shards. I see this set nowhere. Not even in the elasticsearch.yml file. Not even in bin/setenv.) After the upgrade-downgrade exercise I've done, the number of shards has dipped to 5. I've tried various things, like setting it up in the .yml file, using a template as you suggested. Nothing works!
I just need some direction as to how to go back to having 8 shards.