On Wed, Nov 16, 2016 at 02:49:25PM -0500, Stephen Gallagher wrote: > On 11/16/2016 02:40 PM, Vivek Goyal wrote: > > On Wed, Nov 16, 2016 at 02:32:46PM -0500, Daniel J Walsh wrote: > >> We would like to change the docker container storage to default to > >> Overlayfs2 in Fedora 26. But we have a problem on Atomic Host and > >> Fedora Server distributions. > >> > >> > >> Currently docker-storage-setup defaults to devicemapper and is hard > >> coded to setup a thinpool of 40% of remaining disk. Otherwise it sets > >> up loopback devices on the root file system. Devicemapper is nice > >> since it works with thinpools and can automatically expand the storage > >> if the disk space is getting used up. > >> > >> Moving to Overlay, we can more easily use the root file system directly, > >> which would be fine for Fedora Workstation. We want to preserve the use > >> of the remaining storage for Overlay on AH and Fedora Server, since > >> this would give a user flexibility to switch back to using devicemapper > >> if they had problems with the Overlay driver. > > > > And being able to do so basically involves following. > > > > - docker-storage-setup creates a logical volume from free space > > - Creates a filesystem on that logical volume > > - Mounts that logical volume on the directory which docker is going to > > use. > > > > mount /dev/docker-vg/foo /var/lib/docker/ > > > > - Now when docker users overlay2 graph driver, all the images, containers > > and associated metadata will be stored outside the root filesystem and > > onto /dev/docker-vg/foo logical volume. > > > >> We can not as easily > >> support the expanding disk for Overlay since we will not use using thinpool. > > > >> > >> We have looked at options to hard code OverlayFS with the defaults, > > > > If we always mount /var/lib/docker on on /dev/vg/foo for overlay2 driver > > this will be a regression w.r.t current behavior. So I would not > > recommend changing current behavior. I think this should be an opt-in. > > We are working on provide a config knob to elect this behavior and > > atomic host and fedora server will have to opt-in somehow. > > > > I think it will be easy for atomic host as they already drop something > > in /etc/sysconfig/docker-storage-setup. Not sure how fedora server > > variant will do it. > > > > > Today, Fedora Server relies on whatever is the default for docker-storage-setup. > We just tell Anaconda to reserve up to 15GiB by default for the / partition and > then it puts all remaining free space (on drives selected to be used by > Anaconda) into a single logical volume with no partitions. > > It's a very easy thing for us to drop a different config file for > docker-storage-setup into place for Server. So if that's all we need to do, let > me know and I'll work it up. Ok, that sounds good. We are working on providing a knob to opt-in new behavior. I think all you have to drop in config file will be something like. /etc/sysconfig/docker-storage-setup STORAGE_DRIVER=overlay2 YET_TO_BE_NAMED_OPTION=VAL So upstream default will continue to be devicemapper. We will have to modify fedora workstation, fedora server and atomic host infrastructure to opt-in for overlay2. Vivek _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx
