Clarify usage of kernel_release cluster attribute

Since the kernel version of the docker images is not in the expected pattern,
we set a fake kernel value in the `kitchen.docker.yml`to permit to install Lustre on docker.

Signed-off-by: Enrico Usai <[email protected]>

Author: enrico-usai

cookbooks/aws-parallelcluster-environment/attributes/environment.rb

@@ -6,6 +6,8 @@
 default['cluster']['nfs']['threads'] = [[node['cpu']['cores'].to_i * 4, 8].max, 256].min
 
 # Kernel release version used to select Lustre version
+# This is a mechanism used to mock kernel release on docker system-tests, see kitchen.docker.yml:
+# when kernel_release is defined, it will be used, otherwise the release version will be taken from ohai.
 default['cluster']['kernel_release'] = node['kernel']['release'] unless default['cluster'].key?('kernel_release')
 
 # CloudWatch

kitchen.docker.yml

@@ -38,27 +38,29 @@ platforms:
     attributes:
       cluster:
         base_os: alinux2
-        kernel_release: '5.10.157-139.675.amzn2.fake-value'
   - name: centos7
     driver:
       image: <% if ENV['KITCHEN_CENTOS7_IMAGE'] %> <%= ENV['KITCHEN_CENTOS7_IMAGE'] %> <% else %> dokken/centos-7 <% end %>
     attributes:
       cluster:
         base_os: centos7
+        # Since the kernel version of the docker images is not in the expected pattern, set a fake kernel value to permit to install Lustre on docker.
         kernel_release: '3.10.0-1160.76.1.el7.fake-value'
   - name: ubuntu2004
     driver:
       image: <% if ENV['KITCHEN_UBUNTU2004_IMAGE'] %> <%= ENV['KITCHEN_UBUNTU2004_IMAGE'] %> <% else %> dokken/ubuntu-20.04 <% end %>
     attributes:
       cluster:
         base_os: ubuntu2004
+        # Since the kernel version of the docker images is not compatible (6.2.0-1016-azure), set a fake kernel value to permit to install Lustre on docker.
         kernel_release: '5.15.0-1028-aws'
   - name: ubuntu2204
     driver:
       image: <% if ENV['KITCHEN_UBUNTU2204_IMAGE'] %> <%= ENV['KITCHEN_UBUNTU2204_IMAGE'] %> <% else %> dokken/ubuntu-22.04 <% end %>
     attributes:
       cluster:
         base_os: ubuntu2204
+        # Since the kernel version of the docker images is not compatible (6.2.0-1016-azure), set a fake kernel value to permit to install Lustre on docker.
         kernel_release: '5.15.0-1028-aws'
   - name: rhel8
     driver:
@@ -68,11 +70,15 @@ platforms:
     attributes:
       cluster:
         base_os: rhel8
+        # Since the kernel version of the docker images is not in the expected pattern, set a fake kernel value to permit to install Lustre on docker.
+        # Specific kernel versions are not compatible with Lustre.
         kernel_release: '4.18.0-477.13.1.el8_7.fake-value' # Use 477 version to match 8.8 kernel version available on docker
   - name: rocky8
     driver:
       image: <% if ENV['KITCHEN_ROCKY8_IMAGE'] %> <%= ENV['KITCHEN_ROCKY8_IMAGE'] %> <% else %> dokken/rockylinux-8 <% end %>
     attributes:
       cluster:
         base_os: rocky8
+        # Since the kernel version of the docker images is not in the expected pattern, set a fake kernel value to permit to install Lustre on docker.
+        # Specific kernel versions are not compatible with Lustre.
         kernel_release: '4.18.0-477.10.1.el8_8.fake-value'