On Tue, 2014-06-03 at 10:54 -0700, Eric W. Biederman wrote: > Serge Hallyn <serge.hallyn@xxxxxxxxxx> writes: > > > Quoting Pavel Emelyanov (xemul@xxxxxxxxxxxxx): > >> On 05/29/2014 07:32 PM, Serge Hallyn wrote: > >> > Quoting Marian Marinov (mm@xxxxxx): > >> >> We are not using NFS. We are using a shared block storage that offers us snapshots. So provisioning new containers is > >> >> extremely cheep and fast. Comparing that with untar is comparing a race car with Smart. Yes it can be done and no, I > >> >> do not believe we should go backwards. > >> >> > >> >> We do not share filesystems between containers, we offer them block devices. > >> > > >> > Yes, this is a real nuisance for openstack style deployments. > >> > > >> > One nice solution to this imo would be a very thin stackable filesystem > >> > which does uid shifting, or, better yet, a non-stackable way of shifting > >> > uids at mount. > >> > >> I vote for non-stackable way too. Maybe on generic VFS level so that filesystems > >> don't bother with it. From what I've seen, even simple stacking is quite a challenge. > > > > Do you have any ideas for how to go about it? It seems like we'd have > > to have separate inodes per mapping for each file, which is why of > > course stacking seems "natural" here. > > > > Trying to catch the uid/gid at every kernel-userspace crossing seems > > like a design regression from the current userns approach. I suppose we > > could continue in the kuid theme and introduce a iiud/igid for the > > in-kernel inode uid/gid owners. Then allow a user privileged in some > > ns to create a new mount associated with a different mapping for any > > ids over which he is privileged. > > There is a simple solution. > > We pick the filesystems we choose to support. > We add privileged mounting in a user namespace. > We create the user and mount namespace. > Global root goes into the target mount namespace with setns and performs > the mounts. > > 90% of that work is already done. > > As long as we don't plan to support XFS (as it XFS likes to expose it's > implementation details to userspace) it should be quite straight > forward. Any implementation which doesn't support XFS is unviable from a distro point of view. The whole reason we're fighting to get USER_NS enabled in distros goes back to lack of XFS support (they basically refused to turn it on until it wasn't a choice between XFS and USER_NS). If we put them in a position where they choose a namespace feature or XFS, they'll choose XFS. XFS developers aren't unreasonable ... they'll help if we ask. I mean it was them who eventually helped us get USER_NS turned on in the first place. James _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
