[Lxc-users] Kernel 2.6.33-rc6, 3 bugs container specific.
Serge E. Hallyn
serue at us.ibm.com
Tue Feb 2 21:32:54 UTC 2010
Quoting Jean-Marc Pigeon (jmp at safe.ca):
> > I was wondering out loud about the best design to solve his problem.
> > If we try to redirect kernel-generated messages to containers, we have
> > several problems, including whether we need to duplicate the messages
> > to the host container. So in one sense it seems more flexible to
> > 1. send everything to host syslog
> No, if we do that all CONTs message will reach
> the same bucket and it will be difficult to sort
> them out..
> CONT sys_admin and HOST sys_admin could be different
> "entity", so you debug CONT config and critical
> needed information reach HOST (which you do not
> have access to).
Yes, so a privileged task on HOST must pass that information back to
you on CONT. That is not a valid complaint imo. But how to sort the
msgs out is a valid question.
We need some sort of identifier, unique system-wide, attached to.. something.
Is ifindex unique system-wide right now? Oh, IIRC it is, but we wnat it to
be containerized, so that would be a bad choice :)
> > 2. clamp down on syslog use by processes not in the init_user_ns
> Could give me more detail??...
Simplest choices would be to just refuse sys_syslog() and open(/proc/kmsg)
altogether from a container, or to only allow reading/writing messages
to own syslog. (I had hoped to find time to try out the second option but
simply haven't had the time, and it doesn't look like I will very soon.
So if anyone else wants to, pls jump at it...)
Then /proc/kmsg can provide what I described above through a FUSE file,
and if, as you mentioned, the container unmounts the FUSE fs and gets
to real procfs, they just get nothing.
> > 3. let the userspace on the host copy messages into a socket or
> > file so child container can pretend it has real syslog.
> So you trap printk message from CONT on the HOST and
> redirect them on CONT but on a standard syslog channel.
> Seem OK to me, as long /proc/kmsg is not existing
> (/dev/null) in the CONT file tree.
> A bientôt
> Jean-Marc Pigeon Internet: jmp at safe.ca
> SAFE Inc. Phone: (514) 493-4280
> Fax: (514) 493-1946
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