There are several companies that are investing in hybrid and multicloud technologies to achieve high flexibility, that enables you to innovate and meet changing business needs. In these scenarios, customers face the challenge of using IT resources efficiently, in order to best achieve your business goals, implementing a structured IT governance process. This can be achieved more easily if you have solutions that, in a centralized way, allow you to inventory, organize and enforce control policies on your IT resources wherever you are. Azure Arc solution involves different technologies with the aim of supporting hybrid and multicloud scenarios, where Azure services and management principles are extended to any infrastructure. In this article we will explore how, thanks to the adoption of the Azure Guest Configuration Policy it is possible to control the configurations of systems running in Azure, in on-premises datacenters or other cloud providers.
The principle behind Azure Arc
The principle behind Azure Arc is to extend Azure management and governance practices to different environments and to adopt typically cloud solutions, as DevOps techniques (infrastructure as code), also for on-premises and multicloud environments.
Figure 1 – Azure Arc overview
Enabling systems to Azure Arc
Enabling Azure Arc servers allows you to manage physical servers and virtual machines residing outside Azure, on the on-premises corporate network or at another cloud provider. This applies to both Windows and Linux systems. This management experience is designed to provide consistency with Azure native virtual machine management methodologies. In fact, connecting a machine to Azure through Arc is considered in all respects as an Azure resource. Each connected machine has a specific ID, is included in a resource group and benefits from standard Azure constructs such as Azure Policies and tagging.
To offer this experience, the installation of the specific Azure Arc agent is required on each machine that is planned to connect to Azure ("Azure Connected Machine"). The following operating systems are currently supported:
- Windows Server 2008 R2, Windows Server 2012 R2 or higher (this includes core servers)
- Ubuntu 16.04 and 18.04 LTS (x64)
- CentOS Linux 7 (x64)
- SUSE Linux Enterprise Server (SLES) 15 (x64)
- Red Hat Enterprise Linux (RHEL) 7 (x64)
- Amazon Linux 2 (x64)
- Oracle Linux 7
The Azure Arc Connected Machine agent consists of the following logical components:
- TheHybrid Instance Metadata service (HIMDS) that manages the connection to Azure and the Azure identity of the connected machine.
- The Guest Configuration agent that provides in-guest policy and guest configuration features.
- TheExtension Manager agent that manages installation processes, uninstalling and updating machine extensions.
Figure 2 – Azure Arc Agent Components
The Connected Machine agent requires secure outbound communication to Azure Arc on TCP port 443.
This agent provides no other features and does not replace the Azure Log Analytics agent, which remains necessary when you want to proactively monitor the operating system and workloads running on the machine.
For more information about installing Azure Arc, see this official Microsoft document.
Azure Arc-enabled servers can benefit from several Azure Resource Manager-related features such as Tags, Policies and RBAC, as well as some features related to Azure Management.
Figure 3 – Azure Management for all IT resources
Guest Configuration Policy di Azure
Guest Configuration Policies allow you to control settings within a machine, both for virtual machines running in Azure environment and for "Arc Connected" machines. Validation is performed by the client and by the Guest Configuration extension as regards:
- Operating system configuration
- Configuration or presence of applications
- Environment settings
At the moment, most of the Azure Guest Configuration Policies only allow you to make checks on the settings inside the machine, but they don't apply configurations. The exception is a built-in time zone configuration policy operating system for Windows machines.
Requirements
Before you can check the settings inside a machine, through guest configuration policies, you must:
- Enable a’extension on the Azure VM, required to download assigned policy assignments and corresponding configurations. This extension is not required for "Arc Connected" machines as it is included in the Arc agent.
- Make sure that the machine has a system-managed identity, used for the authentication process when reading and writing to the guest configuration service.
Operation
Azure provides built-in specification platform Initiatives and a large number of Guest Configuration Policy, but you can also create custom one both in Windows environment, both in Linux environment.
Guest Configuration policy assignment works the same way as standard Azure Policies, so you can group them into initiative. Specific parameters can also be configured for Guest Configuration Policies and there is at least one parameter that allows you to include Azure Arc-enabled servers. When you have the desired policy definition, it is possible to assign it to a subscription and possibly in a more limited way to a specific Resource Group. You also have the option of excluding certain resources from the application of the policy.
Following the assignment, it is possible to assess the compliance status in detail directly from the Azure portal.
Inside the machine, the Guest Configuration agent uses local tools to audit the configurations:
The Guest Configuration agent checks for new or modified guest policy assignments each 5 minutes and once the assignment is received the settings are checked at intervals of 15 minutes.
The Cost of the Solution
The cost of Azure Guest Configuration Policies is based on the number of servers registered to the service and which have one or more guest configurations assigned. Any other type of Azure Policy that is not based on guest configuration is offered at no additional cost, including virtual machine extensions to enable services such as Azure Monitor and Azure Security Center or auto tagging policies. The billing is distributed on an hourly basis and also includes the change tracking features present through Azure Automation. For more details on costs please visit the Microsoft's official page.
Conclusions
IT environments are constantly evolving and often have to deliver business-critical applications based on different technologies, active on heterogeneous infrastructures and which in some cases use solutions provided in different public clouds. The adoption of a structured IT governance process is easier also thanks to the Guest Configuration Policies and the potential of Azure Arc, that allow you to more easily control and support hybrid and multicloud environments.
