Upgrading the cluster’s underlying OS
Ensure that all your hosts in the cluster are on the operating systems supported with the HDP intermediate bits and Ambari 7.1.x.x before starting the upgrade from HDP 2.6.5.x to HDP intermediate bits.
For many, this is a process that takes time and orchestration between multiple teams within your organization. Two high-level guidelines for moving from one major operating system version to another is as follows:
In-Place and Restore:
Perform an In-place OS refresh and use Ambari Restore Host feature
Move and Decom:
Move Masters and Decom/Recom Workers
Each option has advantages and disadvantages and high-level decision criteria.