Re: [9fans] How to implement a moral equivalent of automounter in Plan9?

["Dan Cross" <crossd@gmail.com>]

On Tue, Dec 2, 2008 at 7:07 PM, erik quanstrom <quanstro@quanstro.net> wrote:
> currently one can prevent external changes to a
> namespace by creating a unique ns with rfork.
> if /proc/$pid/ns were writable, one would not not
> be possible without yet another mechanism.

chmod?  I guess it comes back to, "How do you define external."  If
you mean another process owned by the same user, then it breaks down
(hello trojan horse).

There are many things that would be *possible* with /proc, some of
them ill advised.  For instance, why can't I 'mkdir /proc/n/' and have
it create a new process?  I can think of a number of potential
reasons, one of the most obvious ones is 'how do I choose n';
something more reasonable would probable be a /proc/ctl or /proc/fork
or /proc/new or something that, when read, gives me a file directory
name corresponding to a new process in some 'new' state.  Maybe
copying a binary onto /proc/n/text would and writing 'go' would be the
moral equivalent of a 'spawn'-like call.  Who knows.  I guess the
point is, "what does that *mean*?"  Ie, it would fundamentally change
the process model from something fork-based to something radically
different.  Is that good?  Is that bad?  Beats me.  I'm not sure it's
worth exploring.  I suspect opening up /proc/n/ns for tinkering would
be similar.  As Russ says, no one's felt motivated to do it.  There's
no good reason you can't explore it, but you may find it isn't as cool
as you'd originally hoped.

An aside: One of the nice things about Plan 9 is that a lot of the
things you sort of have to work around in Unix just work in Plan 9.
They applied a few fundamental principles aggressively and in so fixed
a lot of warts that had begun to glare on Unix as it aged.  I can see
the utility of an autofs-like thing, but I wouldn't get too wrapped up
in the semantics of making it look like Unix; that's not a profitable
thing in this environment, since this environment *is* different.
It's funny, the feeling you described when talking about the Sun
intranet is exactly how I felt when first working with plan 9.

That being said, one of the biggest challenges the Linux/Unix
community faces these days is a mental entrenchment and clinging to
bad technology because "that's the way it's always been."  The Plan 9
community should work hard to make sure that doesn't happen to it.

        - Dan C.