[kbenson]

It's all just history now for all I know, but there was work in the past to make Linux containers work on a Solaris fork (SmartOS, specifically) by emulating the Linux syscall table and presenting that to the containers. Joyent did work on this (alas, and there's an excellent and entertaining talk from Bryan Cantrill[1] that goes over it.

I imagine FreeBSD could do something similar if they aren't already. IIRC FreeBSD has a Linux emulation layer (but I don't know how much attention it still gets), and it's had containerization primitives longer than linux, so some amount of filling in the gaps in containerization features and syscall tables (if needed) could possibly yield an OCI compatibility later (for all I know all this already exists).

The problem, and the reason if this doesn't exist why people probably weren't as interested in doing the work, is it would always be "mostly" compatible and working and there would be no guarantee that the underlying software wouldn't exhibit bugs or weird behavior from small behavior differences in the platform when emulating something else. Why open yourself up to the headache when you can just run Linux with containers or build what you want on FreeBSD with jails and their own native containerization primitives.

1: https://www.youtube.com/watch?v=coFIEH3vXPw

[lukeh]

Yeah, emulating syscalls is fine until it isn’t. See WSL1.

[baq]

Some kernels are more similar to others, some are less. Turns out NT is less similar to Linux than required for good performance. I wouldn’t be surprised if Solaris was similar enough given that Linux tries to be Unix-like and Solaris is actually Unix.