Re: [9fans] Backgrounding a task

[Alex Musolino <alex@musolino.id.au>]

> So far, it looks like the closest equivalent is to draw a new window
> and inherit the namespace of the original one by reading the namespace
> from the proc.

The problem with /proc/$pid/ns is entries that can't be "replayed".
For example, the following command will not work:

	mount -b '#|/data' /mnt

Nor does it provide any real indication as to what exactly is hooked
up to the other end of the 9P pipe.

> I wonder if there could be a Rio gesture to draw a new window
> inheriting the namespace of the window I pick by clicking.

Rio can't access the namespaces of the processes running in its
windows.  The -m option to window(1) works by rforking a new process
with the RFNAMEG flag set and then doing the appropriate mounting and
binding to create and use a new rio window.

Some months ago I played with the idea of adding support for an
"nsjoin" command to the /proc/$pid/ctl file.  This allowed you to join
the namespace of another process a little something like this:

	term% ps | grep plumber
	alex            670    0:00   0:00      864K Pread    plumber
	alex            671    0:00   0:00      864K Rendez   plumber
	term% echo nsjoin 670 >/proc/$pid/ctl
	term%

Subsequent changes to the namespace would affect the plumber.  If you
wanted a copy, just do 'rfork n' after joining the namespace.

Of course, a lot of the isolation that per-process namespaces give you
is suddenly undone by the introduction of this facility.  At this
point I'm not entirely convinced that it's worth the trouble.

--
Cheers,
Alex Musolino