add linux only

Author: Justin

articles/aks/security-hardened-vm-host-image.md

@@ -13,12 +13,14 @@ ms.custom: mvc
 
 Azure Kubernetes Service (AKS) is a secure service compliant with SOC, ISO, PCI DSS, and HIPAA standards. This article covers the security hardening applied to AKS virtual machine hosts. For more information about AKS security, see [Security concepts for applications and clusters in Azure Kubernetes Service (AKS)](https://docs.microsoft.com/azure/aks/concepts-security).
 
+> [!NOTE] This document is scoped to Linux agents in AKS only.
+
 AKS clusters are deployed on host virtual machines, which run a security optimized OS which is utilized for containers running on AKS. This host OS is based on an **Ubuntu 16.04.LTS** image with additional security hardening and optimizations applied (see Security hardening details).
 
 The goal of the security hardened host OS is to reduce the surface area of attack and optimize for the deployment of containers in a secure manner.
 
 > [!Important]
-> The security hardened OS is NOT CIS benchmarked. While there are overlaps with CIS benchmarks, the goal is not to be CIS-compliant. The goal for host OS hardening is to converge on a level of security consistent with Microsoft’s own internal host security standards.
+> The security hardened OS is NOT CIS benchmarked. While there are overlaps with CIS benchmarks, the goal is not to be CIS-compliant. The goal for host OS hardening is to converge on a level of security consistent with Microsoft's own internal host security standards.
 
 ## Security hardening features