Hi zimoun,

On Thu, 19 Nov 2020 10:21:16 +0100
zimoun <zimon.toutoune@gmail.com> wrote:

> Let’s postpone this Docker image work and start a new fresh thread once
> v1.2.0 is published and the goal to have something for v1.3.0, well
> that’s my point of view.

After Ryan Prior's E-Mail I'm pretty sure my workaround of creating /tmp,
/etc/passwd, /etc/group etc is what Docker actually expects one to do.

So we can just create those--either at runtime, or maybe even have

  guix system docker-image

do it at build time (if it doesn't already).

I have no opinion on when we should do that (at this release or the next
one), except to state that I am certain that it works (and pretty easily),
because guix-on-docker does that already and guix works just fine there.

That still leaves to explain how to prevent Docker from keeping older layers
when it doesn't need to.

In guix-on-docker I have a Dockerfile like this

FROM alpine:3.12 AS bootstrap-guix-on-alpine
[...]

FROM scratch AS guix-on-docker
COPY --from=bootstrap-guix-on-alpine /etc/guix /etc/guix
COPY --from=bootstrap-guix-on-alpine /var/guix /var/guix
COPY --from=bootstrap-guix-on-alpine /gnu /gnu
COPY --from=bootstrap-guix-on-alpine /usr/local /usr/local
COPY --from=bootstrap-guix-on-alpine /root/.config/guix /root/.config/guix
ADD set-mtimes.scm /
ADD etc/passwd /etc
ADD etc/group /etc
ADD etc/services /etc
ADD with-guix-daemon.scm /
RUN ["/usr/local/bin/guix", "repl", "/set-mtimes.scm"]

in order to prevent Docker from keeping older layers[1].

The "set-times.scm" invocation there is in order to fix the timestamps.

"COPY --from=" does not preserve timestamps.  Then guile is very annoyed
because it can't use any of the ".go" files--because they are older than
the respective ".scm" files.

Using set-times.scm means it will create yet another layer where the only
difference is the timestamps--so it doubles the size of the resulting image.

But then it works.

[1] https://docs.docker.com/develop/develop-images/multistage-build/