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> From an I/O, storage, and memory utilization point of view, it feels baffling to me that containers are so popular.

Why? It's not virtualization, it's containerization. It's using the host kennel.

Containers are fast.

I was referring to the userspace runtime stack, not the kernel. What I criticize is that multiple containers that share a single host usually overdo it with filesystem isolation. Hundreds of MBs of libraries and tools needlessly duplicated, even though they could just as well have used distro packages and deployed their apps as system-level packages and systemd unit files with `DynamicUser=`.

You can hardly call this efficient hardware utilization.

The duplication is a necessity to achieve the isolation. Having shared devels and hordes of unit files for a multi tenant system is hell - versioning issues can and will break this paradigm, no serious shop is doing this.

For running your own machine, sure. But this would become non maintainable for a sufficiently multi tenant system. Nix is the only thing that really can begin to solve this outside of container orchestration.

The isolation is the POINT. You can't be assured that the library and version you need for you app is the same in installed by the system, for example.

And it may not even be installed by the system, hence docker.

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