[Devel] Re: [PATCH 0/2] sys_restore prototype

Serge E. Hallyn serue at us.ibm.com
Tue Jul 29 11:27:46 PDT 2008

Quoting Eric W. Biederman (ebiederm at xmission.com):
> "Serge E. Hallyn" <serue at us.ibm.com> writes:
> > We were talking this morning about what trivial patchset to begin
> > with to get a start on checkpoint and restart.  We thought that
> > rather than start with checkpoint, maybe we should start with
> > something that reads a "checkpoint file" and "restarts" a single
> > task.  In this case, restart means it sets the process id and
> > executes the file which are found in the checkpoint file.
> >
> > So here's what we whipped up for a half hour this morning,
> > and during some of Mark's talk this afternoon.
> >
> > It refuses to run if it isn't the container init, so you must
> > unshare your pidns before calling sys_restore().
> A reasonable approximation. 
> Dave Hansen made a good point when he asked how do we graft a restored
> checkpoint into the rest of the system.  Requiring us to unshare
> everything we intend to unshare before restore achieves this easily,
> and you are following in that model.
> That leads to an interesting implication.  We don't need to set the pid
> of the first process.  At most we can verify that the pid is the same.
> If we have unshared the pid namespace the pid will be 1 and the needed
> pid of the first process will be 1.
> More later.

Good point.  Sounds like our trivial prototype was still way
over-featureful :)

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