31

Plan 9 was developed by Bell Labs as a successor to Unix. Although for various reasons it never quite materialized as such, a fair amount of development still went into Plan 9.

My question is, what - if anything - from Plan 9 has made its way into modern Unix?

Improve this question
2
  • catb.org/~esr/writings/taoup/html/plan9.html Commented Feb 1, 2012 at 21:13
  • 2
    from the paper: "the most dangerous enemy of a better solution is an existing codebase that is just good enough." Commented Apr 6, 2012 at 14:03

5 Answers 5

Reset to default
20

The obvious one is probably UTF-8. But that's probably too obvious.

Al Viro's grand re-architecturing of the Linux VFS is heavily inspired by Plan9. Especially the shift from "Everything Is A File" to "… And Every File Is A Mount Point".

Improve this answer
2
  • 4
    Could you briefly explain (or point me to a resource which explains) what is meant by "...and every file is a mount point"? Commented Feb 28, 2011 at 22:31
  • 5
    @Mr. Shickadance: Traditionally, you can only mount filesystems and you can only mount them on directories. On Linux, you can also mount directories on directories and files on files. So, in a sense, every directory and every file is a filesystem and every file (and not just every directory) is a mountpoint. Example: cd /tmp; echo a > a; echo b > b; sudo mount --bind a b; cat b # => a Commented Mar 1, 2011 at 2:23
19

The clone(2) system call in linux is said to have been modeled after Plan 9's rfork(). (I personally don't see how the timing works out.)

This paper claims that Plan 9 inspired the "mount/filesystem namespace".

The /proc filesystem appears to have come to Plan 9 from 8th Edition Unix, rather than the other way around.

Improve this answer
1
  • It seems that more and more pieces keep coming over but not enough to port native plan9 applications with 100% original functionality. Commented Feb 7, 2016 at 13:28
10

The /proc filesystem in Linux is a Plan 9 idea.

Improve this answer
1
8

Union file systems, such as unionfs and aufs, were inspired by Plan9 union directory mounts.

For example, they are used on live CDs to merge /usr/bin from the CD with a writable file system, so that you can make changes to /usr/bin, even tho the CD is read-only.

Union file systems: Implementations, Part I on lwn.net

For example, if I understand the docs correctly, on Plan9, you could do:

bind -b /usr/bin /bin bind -b /usr/local/bin /bin bind -b /home/username/bin /bin

And all the files in all three directories would appear in /bin (in case of duplicate names, the one in the last-specified directory wins, due to the -b option).

I'm not sure if this is what Bruce means by "mount/filesystem namespace", or is something different.

You could probably also say that sshfs was inspired by Plan9's ftpfs.

Improve this answer
4

In Plan 9, every "filesystem" is implemented by a userspace daemon. (Think FUSE.) These daemons all talk 9P (specifically 9P2000, the second revision of the protocol). 9P is essentially what holds the different parts of the system together.

The v9fs project implements a Linux kernel driver for the 9P protocol. According to the Plan 9 wiki page on it, it is in the mainline kernel as of kernel 2.6.14.

Improve this answer

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.