Re: [vserver] Linux-VServer and net namespaces

From: Daniel Hokka Zakrisson <>
Date: Thu 26 Nov 2009 - 21:11:29 GMT
Message-ID: <43668.>

Grzegorz Nosek wrote:
> 2009/11/26 Daniel Hokka Zakrisson <>:
>>>> /proc/virtual/<xid>/info contains the initpid as
>>>> seen from the host (for init virtualization)
>>> Thanks.
>> Note that most guests actually won't have an init though.
> Well, maybe not sysvinit, but they will have a process that can be
> attached to, no? Persistent contexts (without any process inside)
> might be a problem though.
>>> ip link set dev <interface> netns <pid-of-somebody-in-the-right-namespace>
>>> As iproute isn't exactly well known for heavy layers of abstraction, I
>>> assume this is the interface exposed by the kernel too. Or does
>>> Linux-VServer provide something else?
>> I think we'll have to, since the processes aren't visible from the host,
>> and you can't very well do that from the guest...
> If the point of the pid is to be simply passed to the kernel, I guess
> we'd just need the correct value and the kernel may simply ignore the
> host/guest distinction.

That would be a failure of the isolation, and as such not really an

>>> BTW, Do you foresee any problems with a setup comprising a network
>>> namespace per guest and multiple network contexts inside? As in all
>>> users of a guest share their (virtualised) view of network interfaces,
>>> but still they are limited to different subsets of IP addresses. I'd
>>> really love it.
>> That'll be highly problematic. You cannot manage contexts from within
>> a guest, so you'll need to do the setup on the host as well as putting
>> the processes in the right context. You wouldn't be able to enter or
>> restart services or anything inside the guest.
> Even if I'd create a guest with a netns and a xid but without a nid
> (which is what recent util-vserver does when asked for a netns,
> AFAIK)? I'd like network contexts completely decoupled from "xid"
> contexts.

They are, but the xid context limits capabilities. You have to migrate
to the network context first, since once you're in the xid context,
you can't execute any more vserver(2) commands. And no, enabling a
network namespace will not automatically disable the network context.


> Straying a further bit off topic, did anybody try replacing VServer
> components with mainline features? I.e. using namespaces and cgroups
> instead of VServer contexts?
> Best regards,
> Grzegorz Nosek
Received on Thu Nov 26 21:11:40 2009

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