Re: [tlug] filesystem namespaces

[Uva Coder <uva.coder@example.com>]

On Thu, 3 Mar 2005 13:54:02 +0900, Jim BLACKSON
<blackson@example.com> wrote:
> 
> What is "filesystem namespaces" that Linus talks about?

I was working on a global namespace problem and found this for you.

>>>>> "Pat" == Pat Gunn <pgunn01@example.com> writes:

    Pat> I understand the design philosophy of this, as it would
    Pat> remove the need for a /dev/tty and /dev/fd hack like in Unix,
    Pat> but I'm afraid that I don't see too many other examples where
    Pat> it would be that useful. It seems to fit into the idea of
    Pat> everything being accessable as a file, something that has
    Pat> suited Unix rather well. However, could someone point out
    Pat> some other situations where namespaces in the filesystem are
    Pat> useful (besides emulating chroot) ? That is, is this purely a
    Pat> feature to add consistancy, or am I missing some big point
    Pat> about how this is useful?

Pat,

Plan 9 configurable namespaces are very powerful---when combined with
the 9p protocol.  I'll try to describe an example.

Imagine a small computer -- say in your air conditioner.  It has no ADSL modem
(sic) and so it cannot connect directly to the outside world.  But a
component fails and the air conditioner needs to send an email notice
to the company providing service.  (Let's call the computer AC (get
it?)).  In this example you also have a central computer called HAL.
HAL has an ADSL connection to the outside world.  HAL has /dev/adsl.

AC mounts HAL:/dev/adsl on AC:/dev:adsl.  Now programs on AC can act
as if the ADSL device is local.  Any device that is made available
on the IP network (via 9p protocol on top of IL) to AC looks like
it is local to AC itself.

I hope I've gotten the point across.  This like like NFS, only
better -- like RFS -- only better!  NFS with devices!  Per-process
namespace!

Quentin Fennessy   AMD, Austin Texas

--
I hope this example helps.

-uva