From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <1f9ba332a43a89accc422db5250bae01@9netics.com>
To: 9fans@9fans.net
Date: Sat, 21 May 2016 01:49:13 -0700
From: Skip Tavakkolian <9nut@9netics.com>
In-Reply-To: <CANLPe+O10qVKjd279LshD8PSCpUSQX3TQLyXzpVtMzbMdE975g@mail.gmail.com>
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Subject: Re: [9fans] Namespace inheritance between processes
Topicbox-Message-UUID: 916d8d50-ead9-11e9-9d60-3106f5b1d025

lets create a couple of shell scripts like this:

1) ns_shared:
	#! /bin/rc

	cat /n/tmp/foo
	ramfs -m /n/tmp	# start another ramfs in the child's namespace
	echo something > /n/tmp/foo
	cat /n/tmp/foo
	exit

2) ns_RFNAMEG
	#! /bin/rc

	rfork n
	cat /n/tmp/foo
	ramfs -m /n/tmp	# start another ramfs in the child's namespace
	echo anotherthing > /n/tmp/foo
	cat /n/tmp/foo
	exit

then in an interactive rc:

% ramfs -m /n/tmp
% echo 123 > /n/tmp/foo
% touch /n/tmp/bar
% ls -l /n/tmp
--rw-rw-r-- M 14458 fst fst 0 May 21 01:46 /n/tmp/bar
--rw-rw-r-- M 14458 fst fst 4 May 21 01:45 /n/tmp/foo
% ns_RFNAMEG
123
anotherthing
% ls -l /n/tmp
--rw-rw-r-- M 14458 fst fst 0 May 21 01:46 /n/tmp/bar
--rw-rw-r-- M 14458 fst fst 4 May 21 01:45 /n/tmp/foo
% cat /n/tmp/foo
123
% ns_shared
123
something
% ls -l /n/tmp
--rw-rw-r-- M 14462 fst fst 10 May 21 01:46 /n/tmp/foo
% cat /n/tmp/foo
something
%

> On Sat, May 21, 2016 at 12:26 AM, Casey Rodarmor <casey@rodarmor.com> wrote:
>> Hi 9 fans,
>>
>> I'm trying to figure out how namespace inheritance between process groups works.
>>
>> Let's say I have a process A which forks a child process B with the
>> RFNAMEG so it receives a copy of A's namespace.
>>
>> If process A then makes a change to its namespace, will process B see
>> that change? Or does B receive a distinct copy that A then can't
>> change?
>>
>> Thanks!
>>
>> Best,
>> Casey
>
> Also, whatever the answer is, how can I test this for myself? I was
> struggling to come up with a combination of commands, short of writing
> some C programs, which would let me have two interactive rc shells
> that inherit from one another, since rc doesn't have job control and
> new rio windows are in a new process group.