Already know why Packer is useful? Jump directly to the best practices. When you develop automation, for example, PowerShell Desired State configuration resources, where do you test them? If the answer is locally on your machine or a remote Virtual Machine platform, you are missing out on some opportunities of speed and reduction in your development and test cycle time.
Have a look at Gael Colas’s awesome introduction to Test-Kitchen and Kitchen-DSC, which will show you how to develop and test your DSC resources easily on your local machine inside Virtual Machines.
As part of this workflow, you will need to use a base virtual machine where you apply your DSC configurations too. Depending on your environment, you may need to apply the same DSC resource to multiple machine configurations, for example:. Windows 2012 R2 WMF 4.0 with GUI. Windows 2012 R2 WMF 4.0 Core. Windows 2012 R2 WMF 5.0 with GUI. Windows 2012 R2 WMF 5.0 Core. Windows 2008 R2 WMF 4.0 with GUI. Windows 2008 R2 WMF 4.0 Core. Windows 2008 R2 WMF 5.0 with GUI.
Windows 2008 R2 WMF 5.0 Core. Windows 2016 WMF 5.0 with GUI. Windows 2016 WMF 5.0 Core.
That is 10 different variations of Windows you need to maintain templates for!