On Mon, 2014-05-05 at 17:48 -0400, Richard Guy Briggs wrote:
> On 14/05/05, Serge E. Hallyn wrote:
> > Quoting James Bottomley (James.Bottomley@xxxxxxxxxxxxxxxxxxxxx):
> > > On Tue, 2014-04-22 at 14:12 -0400, Richard Guy Briggs wrote:
> > > > Questions:
> > > > Is there a way to link serial numbers of namespaces involved in migration of a
> > > > container to another kernel? (I had a brief look at CRIU.) Is there a unique
> > > > identifier for each running instance of a kernel? Or at least some identifier
> > > > within the container migration realm?
> > >
> > > Are you asking for a way of distinguishing an migrated container from an
> > > unmigrated one? The answer is pretty much "no" because the job of
> > > migration is to restore to the same state as much as possible.
> > >
> > > Reading between the lines, I think your goal is to correlate audit
> > > information across a container migration, right? Ideally the management
> > > system should be able to cough up an audit trail for a container
> > > wherever it's running and however many times it's been migrated?
> > >
> > > In that case, I think your idea of a numeric serial number in a dense
> > > range is wrong. Because the range is dense you're obviously never going
> > > to be able to use the same serial number across a migration. However,
> >
> > Ah, but I was being silly before, we can actually address this pretty
> > simply. If we just (for instance) add
> > /proc/self/ns/{ic,mnt,net,pid,user,uts}_seq containing the serial number
> > for the relevant ns for the task, then criu can dump this info at
> > checkpoint. Then at restart it can dump an audit message per task and
> > ns saying old_serial=%x,new_serial=%x. That way the audit log reader
> > can if it cares keep track.
>
> This is the sort of idea I had in mind...
OK, but I don't understand then why you need a serial number. There are
plenty of things we preserve across a migration, like namespace name for
instance. Could you explain what function it performs because I think I
might be missing something.
Thanks,
James
> > -serge
> >
> > (Another, more heavyweight approach would be to track all ns hierarchies
> > and make the serial numbers per-namespace-instance. So my container's
> > pidns serial might be 0x2, and if it clones a new pidns that would be
> > "(0x2,0x1)" on the host, or just 0x1 inside the container. But we don't
> > need that if the simple userspace approach suffices)
>
> This sounds manageable...
>
> - RGB
>
> --
> Richard Guy Briggs <rbriggs@xxxxxxxxxx>
> Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
> Remote, Ottawa, Canada
> Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
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