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Comment by icebraining | Hacker News Reader

Docker doesn't use LXC anymore[1]. The reason you need a VM is to get the Linux kernel, not LXC, and the reason you need that is because the macOS kernel (Darwin) doesn't have the necessary containerization features. On FreeBSD, for example, Docker runs natively, without a VM.

[1] https://www.infoq.com/news/2014/03/docker_0_9

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If MacOS doesn't have certain linux kernel features, neither does FreeBSD. How can Docker run on FreeBSD when FreeBSD has no cgroups? I think you misread/misinterpreted your reference.

xhyve and bhyve virtualization built into the BSD kernels. docker for mac now runs a tiny linux vm directly on osx

> How can Docker run on FreeBSD when FreeBSD has no cgroups? I think you misread/misinterpreted your reference.

FreeBSD can run 64 bit and 32 bit Linux binaries via it's Linux emulator[1]. Plus FreeBSD has had containers since FreeBSD 4 which was released in March of 2000, except containers on FreeBSD are called jails.

> If MacOS doesn't have certain linux kernel features, neither does FreeBSD.

Just because one operating system doesn't have a feature that does not mean a different operating system does not have that feature.

[1] https://www.freebsd.org/doc/handbook/linuxemu.html

Jails are considerably different than containers. Jails are more like chroot jails on linux instead.

Edit: My viewpoint was focused more on the composability aspect of containers. But I stand corrected otherwise.

No, jails are basically containers. Docker on FreeBSD uses jails for isolation -- see the wiki page at https://wiki.freebsd.org/Docker

> Jails are considerably different than containers. Jails are more like chroot jails on linux instead.

Thats incorrect both jails and "containers" are examples of OS level virtualization[1]. Instead of virtualizing the hardware you virtualize the operating system, ie system call table.

[1]: https://en.wikipedia.org/wiki/Operating-system-level_virtual...

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