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From: Nicolas Costes (nicolas.costes_at_iut-laroche.univ-nantes.fr)
Date: Thu 01 Sep 2005 - 15:04:03 BST

Le Jeudi 1 Septembre 2005 02:48, Herbert Poetzl a écrit :
> On Wed, Aug 31, 2005 at 04:59:00PM +0200, Nicolas Costes wrote:
> > Le Mercredi 31 Août 2005 10:56, Nicolas Costes a écrit :
> > > Hello, all, I'm still getting a few vserver hosts to production
> > > ;-).. Everything goes fine (There are mainly Samba vservers, not
> > > too hard)
> sounds good!
> but are you sure linux-vserver is the product you
> were looking for? because it seems you might be
> happier with Xen or UML ...

Er.. Why do you say that ?

(Anyway, If it was only for Samba, I would not use vservers. It's mainly
to host side services with spared ressources : DNS slave, Distcc
farm, ... And for security and ease of maintenance)

> > > I'm now trying to setup a Netatalk vserver, and the Appletalk
> > > protocol seems not to be my friend :( . I only managed to run the
> > > afpd service (Afp-over-tcp).
> basically all kind of linux supported protocols
> will work inside a guest, given that they:
> a) that the host can use them quite fine

I tried, it works on the host.

> b) the guest has the proper capabilities

Well, I tried writing CAP_NET_ADMIN and CAP_NET_RAW in the vserver's
bcapabilities file, and this does apparently nothing.

# cat /etc/vservers/filesrv/bcapabilities

I tried too by writing there "NET_ADMIN" and "NET_RAW", there is no error
nor success.

> > > So, My question is : Are the linux-vservers able to host services
> > > other than tcp-based ones ?
> yep, but udp, tcp and special icmp are the only
> ones supported 'by default' ...

Which means ? One has got to activate something to use another protocol ?

> > One more thing : Netatalk tries to load the appletalk kernel module
> > on startup, which apparently fails because being inside a vserver.
> > Anyway, the module is actually loaded when I start or stop the
> > service ! (There is no need for it in the host server, but it appears
> > there to. "One kernel to rule the all", huh ?)
> yep, that's the main idea behind linux-vserver.
> contrary to Xen or UML you have only one kernel
> running on the host, no guest kernel, no guest
> modules jsut pure 100% userspace there ...

This is good ;-) ! But what is fun, is that when /etc/init.d/atalkd is run
(From inside the vserver), it "fails" to load the module, but actually
the kernel loads it at this very moment !!!

Maybe the kernel detects an access to some devices and loads the module
from the host ?

> > But atalkd still fails to start arguing that it cannot find any net
> > device.
> maybe it needs special devices and/or capabilities
> don't know yet, never tried to get it working ...
> but we can investigate this soon, if you find some
> time ...
> > This means the appletalk module isn't working.
> not necessarily, but might be the cause, did you
> load it on the host?

I made many tests of that kind: manually load/Unload the module from the
host (Successes), from the vserver (Fails), unload the module from the
host the launch atalkd in the vserver (The modules is loaded
automagically but atalkd fails), strace atalkd, lauch the vserver's
atalkd from the host - Yes, you read it right ;-),
"/vserver/filesrv/usr/sbin/atalkd" on the command line (This works :-O !)
- etc....

> > As installing a kernel and modules in each of my Mandriva vservers is
> > mandatory, due to dependencies, it may be the wrong module that is
> > loaded... (The host kernel is not the same as the vservers's ones)

> well, guest modules and/or kernels are, as I mentioned
> before, not used/allowed in linux-vserver, did you
> load the guest module on the host?

No. I'll try, but it's bound to fail, no ?

> > I'm stuck there, any idea ?
> did you compile your host kernel (the linux-vserver
> patched one) with appletalk support?

Yes ;-) !

> did you load the proper module and 'configure'
> whatever appletalk requires (on the host)?

Er... Well nothing, but as said above, it works out-of-the box on the
host, even when launching the vserver's atalkd binary on the command line
in the host (I still don't understand how this worked) => So I guess that
the host's default configuration is ok for Appletalk.

> > How are the non-IP protocols handled but linux-vserver ?
> they are not handled at all, most likely you need
> special capabilites (like CAP_NET_RAW) to bind non
> IP sockets ...

Tried this, did not work, but not sure about me doing it well : I read the
Big Weed Page, and the exact syntax for bcapabilities is not given (And I
read the there-linked source file). Moreover, I don't think "vserver ...
start" outputs error message in case of bad config file...

> > Are module loads really allowed ?
> no, they should not be allowed, are they allowed
> for you (inside your guests)?

[root_at_srvfile /]#
insmod /lib/modules/2.6.11-6mdk/kernel/net/appletalk/appletalk.ko.gz
insmod: error inserting
'/lib/modules/2.6.11-6mdk/kernel/net/appletalk/appletalk.ko.gz': -1
Operation not permitted

[root_at_srvfile /]# uname -a
Linux srvfile.foo.com #5 SMP Mon Aug 22 17:33:59 CEST 2005 i686
Intel(R) Pentium(R) III CPU family 1133MHz unknown GNU/Linux

First, the kernel version is not the same that the host's (But that
doesn't seem to be the blocking element here), and moreover, I think the
kernel does its job here in blocking the call ;-)

 (°>   Nicolas Costes
 /|\   IUT de La Roche / Yon
( ^ )  Clé publique: http://www.keyserver.net/
 ^ ^   Musique libre: http://musique-legale.info/ - 

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