[Devel] Re: semantics for namespace naming

[Cedric Le Goater]

Serge E. Hallyn wrote:
> Let's say we have a vserver, from which we start some jobs
> which we want to checkpoint/restart/migrate.  These are two
> of the usages we currently foresee for the namespaces, though
> I'd say it's safe to assume there will be more.
> 
> I'll want to be able to address the c/r jobs by some ID in
> order to checkpoint and kill them.  I'll also want to be
> able to address the entire vserver by some ID, in order to
> kill it.  In that case the c/r jobs should also be killed.
> So those jobs are known by at least two id's.  Furthermore, I
> may want two vservers on the same machine, both running a c/r
> job called 'calculate_pi'.
> 
> So we can look at this as a filesystem.  In the above scenario,
> we've got /sergesvserver, /sergesvserver/calculate_pi,
> /randomvserver, and /randomvserver/calculate_pi.  And, if
> user hallyn logs into /sergesvserver using pam_namespace.so,
> unsharing his mounts namespace to get a private /tmp and /home,
> then he ends up in /sergesvserver/unnamed1.  So each nsproxy
> has a node in the namespace id filesystem, with random names
> unless/until it is renamed to a more meaningful name.  This
> allows us to switch to a vserver by specifying the vserver's
> name (ln /sys/namespaces/vserver1 /proc/nsproxy or whatever
> semantics we end up using), kill an entire vserver recursively
> (rm -rf /sys/namespaces/vserver1), perhaps even checkpoint
> (tar jcf /tarballs/vserver1 /sys/namespaces/vserver1) and
> certainly rename (mv /sys/namespaces/unnamed1 /sys/namespaces/sergeprivhome).
> 
> One key observeration which I haven't made explicit is that you
> never actually leave a nsid ("container").  If you start under
> /vserver1, you will always be under /vserver1.  I don't know of
> any reason that would not be appropriate.  If I start a nested
> vserver from there, then to me it may be known as
> 'vserver_testme', while to the admin of the machine, it would be
> known as /vserver1/vserver_testme.
> 
> This makes one possible implementation of the container struct:
> 
> 	struct container {
> 		struct container *parent;
> 		char *name;
> 		struct nsproxy *nsproxy;
> 		struct list_head children;
> 	};
> 	struct nsproxy {
> 		...
> 		struct container *container;
> 	};
> 
> Plus of course relevant sysfs stuff.

I like the naming model. a few questions :

how do you enter only a subset of namespaces of a nsproxy/container
and not all of it ? 

what flexibility the struct container is giving us ? why not have 
container == nsproxy ? 

the recursivity model looks like extra overhead. it could be flat.

C.

_______________________________________________
Containers mailing list
Containers at lists.osdl.org
https://lists.osdl.org/mailman/listinfo/containers