Comment by bandoti
6 months ago
What about macOS being derived from BSD? Isn’t that where containers came from: BSD jails?
I know the container ecosystem largely targets Linux just curious what people’s thoughts are on that.
6 months ago
What about macOS being derived from BSD? Isn’t that where containers came from: BSD jails?
I know the container ecosystem largely targets Linux just curious what people’s thoughts are on that.
OS X pulls some components of FreeBSD into kernel space, but not all (and those are very old at this point). It also uses various BSD bits for userspace.
Good read from horse mouth:
https://developer.apple.com/library/archive/documentation/Da...
Thank you—I’ll give that a read. :)
„Container“ is sort of synonymous with „OCI-compatible container“ these days, and OCI itself is basically a retcon standard for docker (runtime, images etc.). So from that perspective every „container system“ is necessarily „docker-like“ and that means Linux namespaces and cgroups.
With a whole generation forgetting they came first in big iron UNIX like HP-UX.
Interesting. My experience w/ HP-UX was in the 90s, but this (Integrity Virtual Machines) was released in 2005. I might call out FreeBSD Jails (2000) or Solaris Zones (2005) as an earlier and a more significant case respectively. I appreciate the insight, though, never knew about HP-UX.
https://en.wikipedia.org/wiki/HP_Integrity_Virtual_Machines
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Does it really matter, tho?
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Conceptually similar but different implementations. Containers uses cgroups in Linux and there is also file system and network virtualization as well. It's not impossible but it would require quite a bit of work.
Another really good read about containers, jails and zones.
https://blog.jessfraz.com/post/containers-zones-jails-vms/
BSD jails are architected wholly differently from what something like Docker provides.
Jails are first-class citizens that are baked deep into the system.
A tool like Docker relies using multiple Linux features/tools to assemble/create isolation.
Additionally, iirc, the logic for FreeBSD jails never made it into the Darwin kernel.
Someone correct me please.
> BSD jails are architected wholly differently from what something like Docker provides. > Jails are first-class citizens that are baked deep into the system.
Both very true statements and worth remembering when considering:
> Additionally, iirc, the logic for FreeBSD jails never made it into the Darwin kernel.
You are quite correct, as Darwin is is based on XNU[0], which itself has roots in the Mach[1] microkernel. Since XNU[0] is an entirely different OS architecture than that of FreeBSD[3], jails[4] do not exist within it.
The XNU source can be found here[2].
0 - https://en.wikipedia.org/wiki/XNU
1 - https://en.wikipedia.org/wiki/Mach_(kernel)
2 - https://github.com/apple-oss-distributions/xnu
3 - https://cgit.freebsd.org/src/
4 - https://man.freebsd.org/cgi/man.cgi?query=jail&apropos=0&sek...
Thank you for the links I will take a closer look at XNU. It’s neat to see how these projects influence each other.
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This is great! Thank you!
> what something like Docker provides
Docker isn't providing any of the underlying functionality. BSD jails and Linux cgroups etc aren't fundamentally different things.
Jails were explicitly designed for security, cgroups were more generalized as more about resource control, and leverages namespaces, capabilities, apparmor/SELinux to accomplish what they do.
> Jails create a safe environment independent from the rest of the system. Processes created in this environment cannot access files or resources outside of it.[1]
While you can accomplish similar tasks, they are not equivalent.
Assume Linux containers are jails, and you will have security problems. And on the flip side, k8s pods share UTM,IPC, Network namespaces, yet have independent PID and FS namespaces.
Depending on your use case they may be roughly equivalent, but they are fundamentally different approaches.
[1] https://freebsdfoundation.org/freebsd-project/resources/intr...