After a fresh OS installation or an upgrade to RHEL 7.4, any attempt to install ACFS drivers will fail with the following message: “ACFS-9459 ADVM/ACFS is not supported on this OS version”

The error persists even if the Oracle Grid Infrastructure software includes the  Patch 26247490: 12.2 ACFS MODULE ERRORS & CRASH DURING MODULE LOAD & UNLOAD WITH OL7U4 RHCK.

This problem has been identified by Oracle with  BUG 26320387 – 7.4 kmod weak-modules not checking kABI compatibility correctly

And by Red Hat  Bugzilla bug:  1477073 – 7.4 kmod weak-modules –dry-run changed output format missing ‘is compatible’ messages.

root@oel7node06:/u01/app/12.2.0.1/grid/crs/install# /u01/app/12.2.0.1/grid/bin/acfsroot install
ACFS-9459: ADVM/ACFS is not supported on this OS version: '3.10.0-514.6.1.el7.x86_64'

root@oel7node06:~# /sbin/lsmod | grep oracle
oracleadvm 776830 7
oracleoks 654476 1 oracleadvm
oracleafd 205543 1

The current Workaround consists in downgrade the version of the kmod  RPM to  kmod-20-9.el7.x86_64.

root@oel7node06:~# yum downgrade kmod-20-9.el7

After the package downgrade the ACFS drivers are correcly loaded:

root@oel7node06:~# /sbin/lsmod | grep oracle
oracleacfs 4597925 2
oracleadvm 776830 8
oracleoks 654476 2 oracleacfs,oracleadvm
oracleafd 205543 1