Using docker for clean builds of classic snaps

[Joseph Rushton Wakeling]

On 05/02/17 19:33, Loïc Minier wrote:
> I dont think "snapd" is in the "ubuntu" Docker image which is trimmed down a
> bit

Yes, I gathered that much, which is why my own Dockerfile attempt ensured that 
snapd would be installed with this line:

     RUN apt-get --assume-yes install snapd snapcraft

... but as you say:

> it's also likely that snapd/snaps would hit some technical issues when
> inside Docker. (This might be worth researching/debugging if you're tempted.)

It looks to me like the snapd daemon doesn't actually run inside the container. 
If I try something simple like checking the version of snapd installed, then I 
get this output:

$ sudo docker run -v $PWD:$PWD -w $PWD 592f87a670d0 snap --version
2017/02/05 22:43:59.308309 main.go:220: WARNING: cannot create syslog logger
snap    2.21
snapd   unavailable
series  -

... so it's clearly installed in my custom image, but not started.

If I _do_ try starting it as part of the command to run in the container, I get 
the following:

$ sudo docker run -v $PWD:$PWD -w $PWD 592f87a670d0 systemctl enable --now 
snapd.socket && snap install core && snapcraft clean && snapcraft
error: access denied (try with sudo)

Trying `sudo` (as in `sudo systemctl enable ...`) doesn't seem to make any 
difference.

Any thoughts on what else I could try?  I'm happy to keep exploring myself but 
Docker and sockets aren't really my area of expertise.

I would imagine, though, that the kinds of issues I'm running into with Docker 
are fundamentally the same issues that make it hard for classic snaps to support 
`snapcraft cleanbuild` using lxd ... ?

Thanks & best wishes,

     -- Joe