Subject: Re: [vserver] pam_namespace inside a vserver
From: Wilhelm Meier <wilhelm.meier@fh-kl.de>
Date: Tue, 06 Oct 2009 07:45:55 +0200

Hi again,

Herbert Poetzl schrieb:
> On Mon, Oct 05, 2009 at 07:46:23PM +0200, Wilhelm Meier wrote:
> 
>> we use a vserver as terminal-server, quite a normal setup, i think.
>> The host and guest are both debian lenny.
> 
>> For some reason we need a polyinstantiated /media directory. i would 
>> like to do this with pam_namespace.
> 
> hmm .. could you elaborate on that?
> sounds to me like you want to mount something there?

we use our own netbootet thin-clients (and so called rich-clients). The 
thin-clients can export their local devices (if plugged) via an 
fuse-based filesystem called mediafs. On the terminal-server (vserver) a 
mount is triggered. Up to now the fuse-mount happened in $HOME/remote. 
This is suboptimal for our unskilled users, since they are used to have 
the devices under /media (for the rich-clients or locally installed 
machines).
So we came across the idea to have a session-namespace per login into 
the terminalserver and use then private mounts on /media, so every user 
only sees his/her thin-client devices.

> 
>> When I use pam_namespace in the pamm-session-stack I get the following 
>> error:
> 
>> Oct  5 19:28:23 192.168.222.12 kdm: 
>> rich00E0C5600493.intern.kmux.de:1[27525]: pam_namespace(kdm:session): 
>> Unable to unshare from parent namespace, Operation not permitted
> 
> assuming that the pam module does an unshare with
> CLONE_NEWNS, you can permit that with the context
> capability VXC_NAMESPACE

hmm, the util-vserver from lenny don't support this. I looked into the 
sources (via the link from the great flowers page) and they lack of this 
capability setting (the kernel code contains this flag).


>> It is not clear to me if this is possible, because it would
>> result in somehow nested namespace: the new namespace inside the
>> vserver-namespace?
> 
> a Linux-VServer guest consists of several namespaces,
> the filesystem/mount namespace is only one of them
> and more than that, it is fully hierarchical, so that
> should be fine :)
> 
>> Any hints how to do this?
> 
> get recent and working kernel, use VXC_NAMESPACE

not possible, see above

  be happy :)

yes, I am!

> 
> best,
> Herbert
> 
> if you or your company use and like the Linux-VServer project, 
> why not consider donating hardware or money, or getting a
> service contract with the developers to ensure that it will
> live on and continue to provide high quality free software?
> 
>> -- 
>> Wilhelm

-- 
Wilhelm Meier
An der Sägemühle 9
D-66459 Kirkel