Never grew popular, perhaps. But I'm not sure how it failed, and not sure how many of the Venm Diagrams of concerns plan9 really has with containers.
Yes there was an idea of creating bespoke filesystems for apps, custom mount structures that plan9 had. That containers also did something semi-parallel to. But container images as read only overlays (with a final rw top overlay) feel like a very narrow craft. Plan9 had a lot more to it (everything as a file), and containers have a lot more to them (process, user, net namespaces, container images to pre-assembled layers).
I can see some shared territory but these concerns feel mostly orthogonal. I could easily imagine a plan9 like entity arising amid the containerized world: these aren't really in tension with each other. There's also a decade and a half+ gap between Plan9's hayday and the rise of containers.
Yes there was an idea of creating bespoke filesystems for apps, custom mount structures that plan9 had. That containers also did something semi-parallel to. But container images as read only overlays (with a final rw top overlay) feel like a very narrow craft. Plan9 had a lot more to it (everything as a file), and containers have a lot more to them (process, user, net namespaces, container images to pre-assembled layers).
I can see some shared territory but these concerns feel mostly orthogonal. I could easily imagine a plan9 like entity arising amid the containerized world: these aren't really in tension with each other. There's also a decade and a half+ gap between Plan9's hayday and the rise of containers.