// til · docker · 20 january 2026 · 1 min

TIL: Docker containers aren't virtual machines

A container is a process with isolation. It shares the host kernel. That is why it feels fast and why networking still surprises people.

A VM virtualises hardware and runs a guest kernel. A container is (roughly) a process with namespaces and cgroups. It shares the host’s kernel.

That is why images start quickly. That is why “Windows container vs Linux container” is a real constraint. That is why “the container has its own localhost” still confuses everyone, including me, more often than it should.

I stopped saying “the Docker VM” unless I actually mean Docker Desktop’s Linux VM on macOS/Windows. On a Linux server, there usually is not one.

Found something wrong?

These notes can be incomplete, or wrong in a different environment. Suggest a correction on GitHub or email me at me@t4mer.net.

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TIL: aka.ms is actually a Microsoft domain

A tiny explanation of Microsoft's URL-shortening domain.

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TIL: QML describes the UI tree. C++ still runs the process.

Designer not editing your screen is often the first clue that you are not in a Widgets project.

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TIL: Qt is the toolkit. C++ is the language.

Search results get worse when you ask the toolkit to be a language.