Cause
Upper or mixed case hostname being used, this is being investigated in bug 17580744
Duplicates:
BUG 17666448 - INS-06006 OCCURS IF HOSTNAME IS IN CAPITAL LETTERS FOR GI INSTALLATION
BUG 17675476 - PASSWORDLESS SSH CONNECTIVITY NOT SET UP BETWEEN THE FOLLOWING NODES
Solution
The bug is fixed in 12.1.0.2
The workaround is to either allow OUI or manually (note 300548.1) setup ssh user equivalence for the installing user, then in command line window, ensure ssh doesn't prompt for password for both real hostname and lower case hostname.
For example:
$ ssh RACNODE1 date ====>> real hostname for node1
Fri Aug 8 10:01:03 IST 2018
$ ssh racnode1 date ====>> lower case hostname for node1
Fri Aug 8 10:01:04 IST 2018
$ ssh RACNODE2 date
Fri Aug 8 10:01:05 IST 2018
$ ssh racnode2 date
Fri Aug 8 10:01:06 IST 2018
Fri Aug 8 10:01:03 IST 2018
$ ssh racnode1 date ====>> lower case hostname for node1
Fri Aug 8 10:01:04 IST 2018
$ ssh RACNODE2 date
Fri Aug 8 10:01:05 IST 2018
$ ssh racnode2 date
Fri Aug 8 10:01:06 IST 2018
In the case of upgrade, the alternate workaround is to update inventory to set to lower case nodename instead of real hostname:
$ /oui/bin/runInstaller -updateNodelist ORACLE_HOME= "CLUSTER_NODES={racnode1,racnode2}" CRS=true
Note in above command it's racnode1,racnode2 in lower case despite the hostname is upper case.