> Some Plan 9 ideas have been absorbed into modern Unixes, particularly the more
> innovative open-source versions. FreeBSD has a /proc file system modeled
> exactly on that of Plan 9 that can be used to query or control running
> processes. FreeBSD's rfork(2) and Linux's clone(2) system calls are modeled on
> Plan 9's rfork(2). Linux's /proc file system, in addition to presenting process
> information, holds a variety of synthesized Plan 9-like device files used to
> query and control kernel internals using predominantly textual interfaces.
> Experimental 2003 versions of Linux are implementing per-process mount points,
> a long step toward Plan 9's private namespaces. The various open-source Unixes
> are all moving toward systemwide support for UTF-8, an encoding actually
> invented for Plan 9.
This is interesting. Anyone know of other ways Plan9 has influenced Linux etc. since 2003?
That's probably mostly it. Plan 9 doesn't really have that much in terms of features. It's greatest strength is in how they go together. Having everything as a file is about the only thing I can think of that unixes don't have (which is the most important, yet not initially clearly how, feature).
Oh, and on the programming end maybe the simplified api and CSP based threads/concurrency library.
I would say that union file systems. Recently overlayfs got merged. It doesn't work like Plan9's, but it is probably impossible within POSIX constrains. You probably shouldn't use overlayfs to merge /bin directories so you could get rid of PATH as it is the case in Plan9.
Interesting thing is missing mmap in Plan9. Aside other things it makes most programs work with remote files quite easily. There is no separate path for local and remote files, because either way you have to read/write to them. That also makes local access slower than it can be, but that is the price for network transparency. You can hammer mmap to work with remote files, but it may have too many corner cases. That's at least how I understand it. Please correct me if I'm wrong.
If memory serves Linux is just getting around to proper private/dynamic namespacing as of some recent version, or so I was told by a friend contributing to the kernel. Linux has been slow, but steady at adopting features out of Plan9 as listed in the paste you provided. Most of the features are incomplete once ported, however. All features and the depth of things like /proc aren't fully transferable to *nix due to architecture, kernel design, or other oddities. Plan9's kernel, while small, deviates from most commonly found kernels in that things such as networking are built-in and expected from the moment booting takes place.
