Match Lustre client repo to specific RHEL version

Match Lustre client repo to specific RHEL version which depends on installed kernel, following table reported in https://access.redhat.com/articles/3078#RHEL7

Signed-off-by: Luca Carrogu <carrogu@amazon.com>

Author: lukeseawalker

attributes/default.rb

@@ -212,7 +212,7 @@
       if node['platform_version'].split('.')[1] >= '7'
         # Lustre Client for Centos >= 7.7
         default['cfncluster']['lustre']['public_key'] = 'https://fsx-lustre-client-repo-public-keys.s3.amazonaws.com/fsx-rpm-public-key.asc'
-        default['cfncluster']['lustre']['base_url'] = "https://fsx-lustre-client-repo.s3.amazonaws.com/el/7.#{node['platform_version'].split('.')[1]}/x86_64/"
+        default['cfncluster']['lustre']['base_url'] = "https://fsx-lustre-client-repo.s3.amazonaws.com/el/7.#{get_rhel_kernel_minor_version}/x86_64/"
       elsif node['platform_version'].split('.')[1] == '6'
         # Lustre Drivers for Centos 7.6
         default['cfncluster']['lustre']['version'] = '2.10.6'

libraries/helpers.rb

@@ -307,3 +307,19 @@ def aws_domain
 def platform_supports_pmix?
   node['platform'] != 'centos' || node['platform_version'].to_i > 6
 end
+
+#
+# Retrieve RHEL kernel minor version from running kernel
+# The minor version is retrieved from the patch version of the running kernel
+# following the mapping reported here https://access.redhat.com/articles/3078#RHEL7
+# Method works for minor version >=7
+#
+def get_rhel_kernel_minor_version
+  # kernel release is in the form 3.10.0-1127.8.2.el7.x86_64
+  kernel_patch_version = node['kernel']['release'].match(/^\d+\.\d+\.\d+-(\d+)\..*$/)[1]
+  kernel_minor_version = '7'
+  if kernel_patch_version >= '1127'
+    kernel_minor_version = '8'
+  end
+  kernel_minor_version
+end