You can verify that the permissions required for installing Oracle RAC have been configured on the nodes node1 and node2 by running the following command.
$ ./cluvfy stage -pre dbinst -upgrade -src_dbhome /u01/app/oracle/product/12.1.0/dbhome_1 -dest_dbhome /u01/app/oracle/product/12.2.0/dbhome_1 -dest_version 12.2.0.0.0 -fixup -verbose