Microsoft’s Linux Compatibility Layer and Its Impact on Docker and Cloud Computing

Usually I don’t pay much attention to Microsoft technologies, but the news from Microsoft Build 2016 is worth noting.

People view this news from different angles (see the discussion on Zhihu): Shell enthusiasts hope to use a powerful Linux shell on Windows, and Ruby programmers hope to teach newcomers without forcing an OS change.

However, I think the biggest impact is on Docker; Microsoft’s launch of this technology will help pave the way for Docker on Windows, which may be the direct purpose of this effort.

Let’s look at the specific technology. At first glance it resembles an emulator like Cygwin, or perhaps a virtual machine, but it is actually more direct: it implements Linux system‑call compatibility using the Windows kernel, so performance is considerable (some even believe that implementing epoll with IOCP could outperform native Linux epoll).

Reference the Wikipedia diagram for the architecture:

Windows_2000_architecture.svg.png

We know the WinNT kernel is powerful; its API has an abstraction layer, and the Win32 API can be seen as an implementation of that layer. Theoretically it has no special status, so it can support Linux programs just as it supports native Windows programs. So why haven’t we seen Linux on Windows before?

Technical excellence does not guarantee market acceptance. This design was once considered over‑engineered, and Microsoft did not see much value, so they did not implement a Linux‑API compatible layer.

All of this changed after Docker appeared. In recent years Docker has grown rapidly; it essentially reinvents Linux, which originally had little to do with Microsoft. Yet Docker occupies an important position in cloud computing and drives server‑software development (DevOps), areas Microsoft values, so they began planning to embrace Docker and container technology early on.

Searching Google for “Microsoft + Docker” yields several news items, which are interesting to view together:

Snip20160331_2.png

Notice the dates of those news items. Honestly, when I first saw the earliest news I could not imagine Microsoft would make such a big effort, but their rhythm is clear: first they released a simple Docker CLI with only HTTP wrapping as a test (perhaps to stake a claim), then they combined Windows software’s operation mode with the container trend. Up to now, Microsoft’s approach aligns with Docker, theoretically allowing Windows to run containers and giving Microsoft a share of the server market.

However, there is another difficulty – the kernel. Docker images can span many Linux distributions, but they are limited by the host kernel version, which is why Docker loses some independence compared to virtual machines. Even if Windows Server can act as a container host, it cannot support many Docker images (which are based on Linux) because it lacks the required APIs.

Now Microsoft has filled this gap.

According to current reports, Windows Server will provide Linux‑compatible APIs, so theoretically it can support all existing Docker images, which is very helpful for cloud environments. Because this support is not emulated, Docker’s performance advantage is retained.

From this perspective, the technology dubbed “Win10 and Ubuntu hybrid” is not just a gimmick; it holds an important place in Microsoft’s strategic roadmap. Some friends say Microsoft dug a pit, implying they may not maintain it, but if Microsoft does not abandon it, they should value and improve the technology.

Please follow the WeChat public account devopshub to get more information about DevOps integrated development and operations.