On 05/29/2014 07:32 PM, Serge Hallyn wrote: > Quoting Marian Marinov (m...@1h.com): >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> On 05/29/2014 01:06 PM, Eric W. Biederman wrote: >>> Marian Marinov <m...@1h.com> writes: >>> >>>> Hello, >>>> >>>> I have the following proposition. >>>> >>>> Number of currently running processes is accounted at the root user >>>> namespace. The problem I'm facing is that >>>> multiple containers in different user namespaces share the process >>>> counters. >>> >>> That is deliberate. >> >> And I understand that very well ;) >> >>> >>>> So if containerX runs 100 with UID 99, containerY should have NPROC limit >>>> of above 100 in order to execute any >>>> processes with ist own UID 99. >>>> >>>> I know that some of you will tell me that I should not provision all of my >>>> containers with the same UID/GID maps, >>>> but this brings another problem. >>>> >>>> We are provisioning the containers from a template. The template has a lot >>>> of files 500k and more. And chowning >>>> these causes a lot of I/O and also slows down provisioning considerably. >>>> >>>> The other problem is that when we migrate one container from one host >>>> machine to another the IDs may be already >>>> in use on the new machine and we need to chown all the files again. >>> >>> You should have the same uid allocations for all machines in your fleet as >>> much as possible. That has been true >>> ever since NFS was invented and is not new here. You can avoid the cost of >>> chowning if you untar your files inside >>> of your user namespace. You can have different maps per machine if you are >>> crazy enough to do that. You can even >>> have shared uids that you use to share files between containers as long as >>> none of those files is setuid. And map >>> those shared files to some kind of nobody user in your user namespace. >> >> 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. Thanks, Pavel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
