F26 Self Contained Change: Docker Overlay 2

[Jan Kurik]

= Proposed Self Contained Change: Docker Overlay 2 =
https://fedoraproject.org/wiki/Changes/DockerOverlay2

Change owner(s):
* Lokesh Mandvekar <lsm5 AT fedoraproject DOT org
* Dan Walsh <dwalsh AT redhat DOT com>


Change the default Docker Storage to be overlay2 .



== Detailed Description ==
Upstream docker is moving to overlay2 by default for its storage. We
plan on following suit. There are some performance advantages of
overlay2 over devicemapper in memory sharing, which we would like to
take advantage of. We now have SELinux support for Overlay file
systems, so the security should be just as good.

Note: Overlay is not a Posix Compliant file system, so there could be
problems with your containers running on overlay, so we want to make
sure it is fairly easy to switch back to devicemapper.

Devicemapper out of the box, on Fedora Workstation, currently defaults
to loopback devices for storage, which has a performance penalty, but
this was the only way we were able to get docker to work right away.
Switching to overlay2 will cause the storage to be shared with / and
will eliminate this performance overhead. This is the way we will ship
Fedora Workstation.

On Fedora atomic host and Fedora server we have been storing
devicemapper storage on a separate partition. We plan on doing the
same thing with overlay2. This means separate device will be mounted
on /var/lib/docker. This will make it easier for someone to switch
back to devicemapper, if overlay2 has problems.

Upgraded systems will not be effected.

If you want to switch from one storage to another take a look at the
`atomic storage` commands.

We will write up release notes to cover this change. Along with a blog
explaining the commands to switch back and forth.




== Scope ==
* Proposal owners:
Implementation of this Change

* Other developers:
N/A (not a System Wide Change)

* Release engineering:
N/A (not a System Wide Change)

* List of deliverables:
N/A (not a System Wide Change)

* Policies and guidelines:
N/A (not a System Wide Change)

* Trademark approval:
N/A (not needed for this Change)
-- 
Jan Kuřík
Platform & Fedora Program Manager
Red Hat Czech s.r.o., Purkynova 99/71, 612 45 Brno, Czech Republic

[Matthew Miller]

On Thu, Jan 19, 2017 at 08:36:02AM +0100, Jan Kurik wrote:
>  Change the default Docker Storage to be overlay2 . 
I made a couple of edits to this, mostly clarifying that overlay2 is
not a second overlay filesystem, but a second Docker driver for the
same OverlayFS.

-- 
Matthew Miller
<mattdm(a)fedoraproject.org&gt;
Fedora Project Leader

[Daniel J Walsh]

On 01/19/2017 09:20 AM, Matthew Miller wrote:
>  On Thu, Jan 19, 2017 at 08:36:02AM +0100, Jan Kurik wrote:
> > Change the default Docker Storage to be overlay2 .
>  I made a couple of edits to this, mostly clarifying that overlay2 is
>  not a second overlay filesystem, but a second Docker driver for the
>  same OverlayFS.
>  
Sounds good to me.