Re: [atomic-devel] Fedora 26 change: using overlayfs as default

[Daniel J Walsh <dwalsh redhat com>]

On 12/15/2016 12:18 PM, Josh Berkus wrote:
> Dan, Dusty, Vivek:
>
> So far nobody has defined (technically) the exact problem with overlayfs
> and how it affects applications which want to write data inside the
> container.
>
> Note that just saying "don't use Overlay for persistent data" really
> isn't good enough.  Apps in containers frequently write data to places
> users aren't aware of, such as writing port information to /var/run.
> While this data may not be important to the user, the app will fail if
> it errors out.
>
> Pushing a change which will cause 30% of a user's containers to start
> failing for reasons which are opaque to them is not something we should
> do lightly.
>
Josh.  More likely this will cause .0001% of users to fail.  But it is
not a Posix
compliant database, so their could be issues. 

Only other issues I know of now are the handling of "special" files things
like sock_files, character devices etc.  But these should almost always
be on
tmpfs places like /dev and /run.