[Automated-testing] Exporting an OverlayFS as NFS

[Kevin Hilman]

On Fri, Feb 16, 2018 at 10:38 AM,  <Tim.Bird at sony.com> wrote:

>> -----Original Message-----
>> From: Kieran Bingham on Friday, February 16, 2018 1:24 AM
>> Hi Farmers:
>>
>> In the recent LWN article: https://lwn.net/Articles/746791/ there is an
>> excerpt
>> highlighting that Overlay file systems can now (or will soon) export over
>> NFS...
>>
>> I've been waiting for this for a long time...:
>
> ... [interesting bits clipped]
>
>> Only really posting this to raise awareness of what I think is a very useful
>> feature coming to us in v4.16 - and perhaps raise some discussion on desired
>> features - or perhaps to discover that no one really uses NFS root anymore;
>> because 96boards didn't put an Ethernet connector on the design.
>>
>>
>> I think there's certainly scope to build some useful tools on top of NFS
>> exported overlays though.
>
> This is an interesting development.  Thanks for sharing it.
>
> I used to use NFS extensively in my previous farm.  I don't use it as much in my current
> farm as I now run more benchmarks, and having the filesystem be over NFS skews the
> results of some of them.

The other problem with NFS is doing anything with secure attributes
doesn't work.  I've switched to using NBD for filesytems with
security.  I'll have to have a look to see if overlayfs could be
combined with NBD in some way.

FWIW, LAVA already supports the notion of overlays in a few different
ways.  First, you can pass a rootfs image as well as (multiple)
overlay images in the job file.  I think it will simply unpack/untar
them in order.  However, unpacking an overlay on top of a filesystem
with secure attributes causes problems too, so LAVA provides a generic
mechanism for the DUT itself to fetch overlays after its booted up.
This can be useful if the DUTs all boot a standard rootfs, but then
can download an overlay that has custom test suites etc.

As usual, (too) many options,  :)

Kevin