Quoting Miklos Szeredi (miklos@xxxxxxxxxx): > > > Thinking a bit more about this, I'm quite sure most users wouldn't > > > even want private namespaces. It would be enough to > > > > > > chroot /share/$USER > > > > > > and be done with it. > > > > > > Private namespaces are only good for keeping a bunch of mounts > > > referenced by a group of processes. But my guess is, that the natural > > > behavior for users is to see a persistent set of mounts. > > > > > > If for example they mount something on a remote machine, then log out > > > from the ssh session and later log back in, they would want to see > > > their previous mount still there. > > > > > > Miklos > > > > Agreed on desired behavior, but not on chroot sufficing. It actually > > sounds like you want exactly what was outlined in the OLS paper. > > > > Users still need to be in a different mounts namespace from the admin > > user so long as we consider the deluser and backup problems > > I don't think it matters, because /share/$USER duplicates a part or > the whole of the user's namespace. > > So backup would have to be taught about /share anyway, and deluser > operates on /home/$USER and not on /share/*, so there shouldn't be any > problem. In what I was thinking of, /share/$USER is bind mounted to ~$USER/share, so it would have to be done in a private namespace in order for deluser to not be tricked. > There's actually very little difference between rbind+chroot, and > CLONE_NEWNS. In a private namespace: > > 1) when no more processes reference the namespace, the tree will be > disbanded > > 2) the mount tree won't be accessible from outside the namespace But it *can* be, if properly set up. That's part of the point of the example in the OLS paper. When a user logs in, sshd clones a new namespace, then bind-mounts /share/$USER into ~$USER/share. So assuming that /share/$USER was --make-shared'd, it and ~$USER are now in the same peer group, and any changes made by the user under ~$USER will be reflected back into /share/$USER. > Wanting a persistent namespace contradicts 1). Not necessarily, see above. > Wanting a per-user (as opposed to per-session) namespace contradicts > 2). The namespace _has_ to be accessible from outside, so that a new > session can access/copy it. Again, I *think* you are wrong that private namespace contradicts this requirement. > So both requirements point to the rbind/chroot solution. It all points to a combination of the two :-) -serge - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
