Umm yes please. It's really difficult to describe how much this would help the OOTB experience for folks getting started.
On Mon, Aug 8, 2016 at 8:06 AM, Colin Walters <walt...@verbum.org> wrote: > Upstream docker has a decent page: > https://docs.docker.com/engine/userguide/storagedriver/selectadriver/ > > (One thing they don't mention explicitly though is the page cache > sharing that overlayfs has over devicemapper or btfs, which can be > substantial) > > Though the patches to use overlayfs with SELinux are still experimental, > and > not yet in our CentOS stream, I'd like to lay the groundwork for it. > > In particular, overlayfs has a significant reduction in "administrative > cognitive overhead", since we can default to one LV+filesystem for > the OS that encompasses both the OS (yum/ostree) data and container > images, and hence not have to juggle LV sizes. > > Another way to look at this is it makes "yum install docker" on CentOS 7 > work with a single disk default. > > This is all related to single node - and there are a lot of potentially > better way to manage images in a cluster, but the single node experience > is important too. It's relevant both for desktop systems that use Docker > and > Vagrant boxes, etc. > > To that end: > https://github.com/CentOS/sig-atomic-buildscripts/pull/134 > landed, which ensures that newly formatted xfs filesystems are compatible. > > Our CI then updated the installer and cloud images, so I verified that > the vagrant-libvirt box here: > https://ci.centos.org/artifacts/sig-atomic/centos-continuous/images/cloud/ > latest/images/ > has: > > # xfs_info /|grep ftype > naming =version 2 bsize=4096 ascii-ci=0 ftype=1 > > There's a number of TODOs here like making it easier to default to > overlayfs from Anaconda/kickstart. > > But I think the important thing for us to flesh out better is transition > paths. Obviously, one can just reinstall a node. Many environments will > be set up to do that, but we should also support transitioning a dm to > overlay > when one doesn't want to reinstall. > > I've verified that from a current CentOS AH Alpha, I can: > > systemctl stop docker > rm /var/lib/docker/* -rf > # (configure docker to use overlay) > lvm lvremove atomicos/docker-pool > lvm lvcreate -n docker-images -L 10G atomicos # (TODO: also tweak this to > auto-grow?) > mkfs.xfs -n ftype=1 /dev/mapper/atomicos-docker--images > mount /dev/mapper/atomicos-docker--images /var/lib/docker > # (add that to /etc/fstab too) > systemctl start docker > > This keeps the atomicos/root LV with an old-format XFS filesystem and > won't give you a unified storage pool, but does give you the runtime > advantages of overlay. > > -- Cheers, Timothy St. Clair tstcl...@redhat.com
