During my last session preparation, I switched Docker for Windows to use Windows containers, to be honest I don’t have use it for some times (my nested virtualized Windows Server 2016 do the job) and I had the following error when downloading the microsoft/nanoserver image : unknow blob

The issue may be that your Docker for Windows daemon is not completely switch to Windows container. So execute the following line to switch it : & ‘C:\Program Files\Docker\Docker\DockerCli.exe’ –SwitchDaemon

Then pull your image again and things should work :