On Tue, Sep 04, 2012 at 12:46:05PM -0700, Eric W. Biederman wrote: > "Serge E. Hallyn" <serge@xxxxxxxxxx> writes: > > > Quoting Glauber Costa (glommer@xxxxxxxxxxxxx): > >> Not all files provided by the kernel are "per-kernel". /proc/self is > >> full of per-namespace stuff. > >> > >> >> The way I see it, every file we need to setup from the outside is a > >> >> hassle. Among many other things, it is just asking for duplication of > >> >> efforts among multiple userspaces. > >> >> > >> >> netns does this for its proc files. The only reason we don't do it for > >> >> cgroups-driven file, is that the semantics is very ill-defined. For this > >> >> file, it doesn't seem to be the case. > >> > > >> > But it is the case. How do you intend to have the kernel decide what > >> > value to put in there for a process in a container, or in a chroot? > >> > > >> > >> one value per pidns. > > > > ok. (So should it be called /proc/pidns_uuid? Well, whatever. No > > objection from me - thanks.) > > /proc/sys/kernel/boot_id. > > Someday we will get the plumbing right in the kernel so that can be > /proc/sys -> /proc/self/sys and /proc/self/sys/kernel/boot_id > > The origin of boot_id was so that emacs could implement distributed > locking in userspace by creating a symlink from .#filename to > user@xxxxxxxxxxxx:boot_id. > > Ultimately emacs opted to just stat /var/run/random-seed or to grovel > through utmp or wtmp to find the last boot record. > > Of course /var/run/random-seed is now named something like > /var/lib/urandom/random-seed as distributions continue their relentless > pursuit to break userspace. > > But ultimately boot_id was defined as something you can use to detect > stale pids and stale lockfiles. Since the original definition was > a uuid to detect stale pids, that seems a reasonable justification > for keeping it in the pid_namespace. Boot_id isn't the best name in > that case but shrug. Ok, so reading through this thread, my understanding is that any patch for this needs to work as follows: - Associate '/proc/sys/kernel/random/boot_id' with the pid namespace - Allow boot_id to be written to, only if it has not yet been read in the current pid namespace. (for migration use case) - Lazy generate a UUID for boot_id on first read in the current pid namespace, only if it has not previously been written to. - Add file to Documentation/ explaining the use case for the boot_id file and its semantics wrt to namespaces. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
