For IBM Power servers, only RHEL 7.4 or 7.5 are supported.
https://docs.hortonworks.com/HDPDocuments/Ambari-2.7.1.0/bk_ambari-installation-ppc/content/operatin...
Operating Systems Requirements
The following, power operating system is supported:
- Red Hat Enterprise Linux (RHEL) v7.4, v7.5
 | Important |
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The installer pulls many packages from the base OS repositories. If you do not have a complete set of base OS repositories available to all your machines at the time of installation you may run into issues. |
If you encounter problems with base OS repositories being unavailable, please contact your system administrator to arrange for these additional repositories to be proxied or mirrored.