The New Serial Console Access in Azure VMs


Recently the Azure compute team announced Serial Console Access for Azure Virtual Machines (currently in public preview).

The Serial Console Access is available for both Windows and Linux virtual machines.

But what exactly is serial access and how can it benefit your Azure solution? Read on and I will try to give you some answers.

What is a serial console?

So, how do you access a virtual machine in the cloud when no network connection works? The answer is often: you don’t.

Often you start over with a new VM or with the latest backup. Back in the ‘old’ days when we had on-prem data centers, you could walk up to the physical server and attach keyboard/mouse, or you could set up a serial connection. The latter is now possible with Azure Serial Console Access. Serial access is built right into modern versions of Windows Server as the feature called ‘Serial Access Console’ which is part of ‘Emergency Management Services Toolbox‘ (EMS).

Inside EMS and SAC

Under the hood, EMS enables the ‘Serial Access Console‘ (SAC). SAC is a special command-line utility that runs almost independently (!) of Windows itself. SAC runs even when Windows doesn’t. For instance, with SAC you can interact with a Windows server even after it has gone into BSoD (Blue Screen of Death) of some other flavor of Windows-freeze. You can also connect to the server during boot before Windows has even started.

Besides the SAC-specific commands like ‘crashdump‘, you can also start up a Windows command prompt (CMD). And apparently also a PowerShell prompt (supposedly only when Windows is actually running)

This kind of administration is often referred to as out-of-band administration.

In Google Cloud Platform it has been possible to interact with the serial console for some time with support for both the GCP command-line utility and through the GCP Console (‘GCP Portal’) so it will be exciting to see how Azure Serial Console Access will stack up against the competition.







Photo by blakespot