Editing Cluster Operations (section)

=== Shut Down/Restart Nodes ===
Now that things have settled out, we can stop/restart the opensearch services.  Note that a full cluster shutdown should be avoided, since any activity on the cluster as it is going down or coming up could cause errors to the user.  Use the systemd commands to stop/start/restart the nodes:
 # do this on all nodes
 sudo systemctl stop opensearch
  ... do required activity on all nodes ...
 sudo systemctl start opensearch
... or ...
 # restart a single node
 sudo systemctl restart opensearch
If it was a complete cluster shutdown, all nodes must rejoin the cluster before proceeding.  In either case, wait until the cluster (or node) achieves a "YELLOW" state before proceeding ... this means that all primary shards are accounted for, but replicas may not be.