Windows Server Containers is an OS virtualization technology from Microsoft that is available from Windows Server 2016 onwards. Windows Server Containers are lightweight processes that are isolated from each other and have a similar view of the OS, processes, filesystem, and network. Technically speaking, Windows Server Containers are similar to Linux containers, which we discussed earlier. The only difference being the underlying kernel and workloads that run on these containers. The following image describes Windows Server Containers:
Here's a little background about Windows Server Containers:
- Microsoft's research team worked on a program called Drawbridge for bringing the famous container technologies to Windows Server ecosystem
- In the year 2014, Microsoft started working with Docker to bring the Docker technology to Windows
- In July 2015, Microsoft joined Open Container Initiative (OCI) extending its support for universal container standards, formats, and runtime
- In 2015, Mark Russinovich, CTO at Microsoft Azure, demonstrated the integration of containers with Windows
- In October 2015, Microsoft announced the availability of Windows Server with containers and Docker support in its new Windows Server 2016 Technical Preview 3 and Windows 10
Microsoft adapted Docker in its famous Windows Server ecosystem so developers can now develop, package, and deploy containers to Windows/Linux machines using the same toolset. Apart from support for the Docker toolset on Windows Server, Microsoft is also launching native support to work with containers using PowerShell and Windows CLI. Since OS virtualization is a kernel level feature there is no cross platform portability yet, which means a Linux container cannot be ported to Windows or vice versa.
Windows Server Containers are available on the following OS versions:
- Windows Server 2016 Core (no GUI): A typical Windows Server 2016 server with minimal installation. The Server Core version reduces the space required on disk and the surface of attack. CLI is the only tool available for interacting with the Server Core, either locally/remotely. You can still launch PowerShell using the
start powershellcommand from the CLI. You can also callget-windowsfeatureto see what features are available on Windows Server Core. - Windows Server 2016 (full GUI): This is a full version of Windows Server 2016 with standard Desktop Experience. The server roles can be installed using Server Manager. It is not possible to convert Windows Server Core to full Desktop Experience. This should be a decision taken during installation only.
- Windows 10: Windows Server Containers are available for Windows 10 Pro and Enterprise versions (insider builds 14372 and up). The containers and Hyper-V/virtualization feature should be enabled before working with containers. Creating container and images with Windows 10 will be discussed in following chapters.
- Nano Server: Nano Server is a headless Windows Server 30 times or 93% smaller than the Windows Server Core. It takes far less space, requires fewer updates, high security, and boots much faster than the other versions. There is a dedicated chapter in this book on working with Nano Servers and Windows Containers.
The most important part is that Windows Server Containers are available in two flavors, Windows Server Containers and Hyper-V Containers. All of the previously mentioned OS types can run Windows Server Containers and Hyper-V Containers. Both the containers can be managed using Docker API, Docker CLI, and PowerShell.