Is there a way to do in-place update the OS of an Azure VM, from within the Azure Portal?
i.e. from Windows Server 2012 R2 to Windows Server 2016
Nope. As per official article:
Microsoft does not support an upgrade of the operating system of a Microsoft Azure virtual machine. Instead, you should create a new Azure virtual machine that is running the supported version of the operating system that is required and then migrate the workload.
https://support.microsoft.com/en-us/help/2721672/microsoft-server-software-support-for-microsoft-azure-virtual-machines
Instead, use the Windows Server Migration Tools to assist you in roles and features migration:
Install, use, and remove Windows Server migration tools
No, there is no such ability to upgrade an OS on the Azure VM (and not that I heard about it in future, who knows thou).
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With