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Comment by tyingq | Hacker News Reader

The 9p filesystem found its way into KVM's VirtFS. Curious if there's other active places where parts of Plan 9 are being used.

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The original Cisco PIX firewall used modified Plan 9 as the operating system. In fact, despite the official history, the name PIX came from Plan 9, or Plan IX. I know this because the person who wrote the entire PIX software stack, Brantley Coile, told me.

Much of the Golang toolchain came from Plan 9:

https://news.ycombinator.com/item?id=8817990

EDIT: and the Gopher mascot was designed by Reneé French who also designed Glenda the Plan 9 bunny:

https://golang.org/doc/faq#gopher

Shoot, much of the Go lang team came from Plan 9. And they brought a lot of code and ideas with them.

Currently on my mind os `os.FileMode`; here's a comment I wrote in some Go code that interfaces with Python:

    // A StatMode represents a file's mode and permission bits, as represented in Python
    // (i.e. `os.stat()`'s `st_mode` member).  Similar to how Go's `os.FileMode` assigns bits to have
    // the same definition on all systems for portability, Python's `stat` assigns bits to have the same
    // definition on all systems for portability.  And it just so happens that Go's bits match those of
    // Plan 9, and Python's bits match those of the Linux kernel.
    type StatMode uint16

PS: If you weren't aware, Renée French's connection to Plan 9 and Go is largely that she's married to Rob Pike.

I did not know the about Reneé and Rob! Thanks!

The image and image/draw package design[1] is also inspired by Plan 9.

[1] https://blog.golang.org/image-draw

It's used, bizarrely enough, to communicate between the Windows and Linux sides of Windows Subsystem for Linux 2 - if I remember correctly, it's used to expose NTFS to the Linux side.

And in roughly the same role (Host FS parts exposed to the VMs) in ChromeOS's Crostini container runtime.

https://chromium.googlesource.com/chromiumos/docs/+/HEAD/con...

Isn't WSL using 9p to mount the linux fs on windows side? https://devblogs.microsoft.com/commandline/whats-new-for-wsl...

Why is the 9P filesystem used to frequently for these applications? Is it just that much better than the alternatives?

In general, 9P2000 is simple and fairly elegant. If you don't need POSIX semantics (and fs metadata), it's really quite simple to implement. For a bit more cost in terms of complexity you can go for 9P2000.u which makes things POSIXy enough if you've got a single client (as you do with VM -> host). This is great if you want to provide virtual filesystems, either proxied from the host or backed by something more exotic. In addition to QEMU, the gVisor folks (https://gvisor.dev/) have made heavy use of 9P (with enhancements) for similar reasons (in addition to Google being generally populated with Plan 9 aficionados).

Then, there's 9P2000.L... This has that "let's just take the filesystem vtable and export it as a protocol" flavor. This works well enough on Linux if you're just looking to translate the calls over into syscalls. I wouldn't recommend implementing a bespoke server for it, though. You're better off just implementing things with FUSE.

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