Re: [vserver] /proc/net/dev missing when networknamespaces are active

From: Herbert Poetzl <>
Date: Thu 28 Jun 2012 - 00:26:58 BST
Message-ID: <>

On Wed, Jun 27, 2012 at 05:19:24PM +0200, Adrian Reyer wrote:
> On Wed, Jun 27, 2012 at 04:25:07AM +0200, Herbert Poetzl wrote:
>>>> - The simple trick of bind-mounting a suitable directory
>>>> on /proc/net works in a very limited way as /proc/net is a
>>>> symlink to /proc/self/net
>>> I think you should never try that.
>>> When mount bind you effectively use the deferent network
>>> namespace for the new namespace in teh vserver.
>> you cannot bind mount across namespaces (atm)

> And I didn't try that. The tools (ifconfig, netstat, isc-dhcpd)
> complained about a missing /proc/net/dev. The content
> of that file is quite generic, so I created a directoy
> '/some/where/vproc/net', stuffed a file 'dev' in it, copied the
> intresting part of my hosts net-file in there and bind mounted
> that.

> However, as it is not /proc/net but /proc/self/net and
> therefore a movin target it failed.

>> there is no old/obsolete approach to enabling namespaces
>> and I'm pretty confident util-vserver does nothing wrong
>> here

> Usually I use network isolation and am quite happy with it.
> I this case I need a namespace. util-vserver should
> unshare the network namespace when it find a file
> /etc/vservers/NAME/spaces/net and it does at least something
> like that. However, the result is completly different from what
> you get with e.g. the 'unshare' command line tool. Especially
> /proc/net is missing.

>> I'm happily using Linux-VServer together with kvm on a
>> routed as well as bridged setup and never encountered
>> any issues (why would there be any? Linux-VServer does
>> not mess with layer 2)

> So do I, I'd assume Steve misses something like
> echo 1 > /proc/sys/net/ipv4/conf/default/promote_secondaries
> echo 1 > /proc/sys/net/ipv4/conf/all/promote_secondaries

>>> The problem is gone away currently with my LXC containers setup.

>>> I do hope that the vserver devs fix the bug so I can use
>>> network ns again with vserver.
>> please elaborate what 'the bug' is in your opinion and
>> describe the setup where 'you used network namespaces with
>> Linux-VServer'

> The bug is the missing /proc/net/dev and actually the whole of
> /proc/net when using network namespaces with linux-vserver via
> /etc/vservers/NAME/spaces/net.

> /proc/net is fine with 'unshare' without vserver as well
> as with vserver with network isolation and without network
> namespaces.

are you sure you unshared a new network namespace?

what is the exact command you use (with unshare) and
what does strace -fF say on that command?


> Regards,
> Adrian
> --
> LiHAS - Adrian Reyer - Hessenwiesenstraße 10 - D-70565 Stuttgart
> Fon: +49 (7 11) 78 28 50 90 - Fax: +49 (7 11) 78 28 50 91
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Received on Thu Jun 28 00:27:13 2012

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