Re: [Qemu-devel] [PATCH 04/23] docker: compact debian base

[Philippe Mathieu-Daudé]

On 05/08/2017 08:04 AM, Alex Bennée wrote:
> Philippe Mathieu-Daudé <address@hidden> writes:
>
> > - install common/basic tools at once
> > - one-line Emdebian setup
> > - use eatmydata and remove apt cache to save space
> > - add bison and flex and git
> >
> > Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> > ---
> >  tests/docker/dockerfiles/debian.docker | 22 ++++++++++++----------
> >  1 file changed, 12 insertions(+), 10 deletions(-)
> >
> > diff --git a/tests/docker/dockerfiles/debian.docker 
> > b/tests/docker/dockerfiles/debian.docker
> > index 52bd79938e..694f8d3b63 100644
> > --- a/tests/docker/dockerfiles/debian.docker
> > +++ b/tests/docker/dockerfiles/debian.docker
> > @@ -9,17 +9,19 @@
> >  #
> >  FROM debian:stable-slim
> >
> > -# Setup some basic tools we need
> > -RUN apt update
> > -RUN apt install -yy curl aptitude
> > -
> > -# Setup Emdebian
> > -RUN echo "deb http://emdebian.org/tools/debian/ jessie main" >> 
> > /etc/apt/sources.list
> > -RUN curl http://emdebian.org/tools/debian/emdebian-toolchain-archive.key | 
> > apt-key add -
> > +# Install some basic tools and common build utilities
> > +RUN apt-get update && \
> > +    DEBIAN_FRONTEND=noninteractive apt-get install -yy \
> > +        eatmydata && \
>
> I wonder if we should just use ENV instead to set DEBIAN_FRONTEND?

In https://github.com/moby/moby/issues/4032#issuecomment-34597177 Tianon 
Gravi commented:

[...] setting it via ENV should be actively discouraged. [...]
The reason it's not a good default is that if I docker run -i -t ... 
bash, I'm now interactive, and this variable being set is very, very wrong.

> > +    DEBIAN_FRONTEND=noninteractive eatmydata apt-get install -y 
> > --no-install-recommends \
> > +        curl aptitude \
> > +        build-essential clang git \
> > +        bison flex && \
> > +    rm -rf /var/lib/apt
>
> Use apt clean to do this.

Ok.

> >  # Duplicate deb line as deb-src
> >  RUN cat /etc/apt/sources.list | sed "s/deb/deb-src/" >> /etc/apt/sources.list
> >
> > -# Install common build utilities
> > -RUN apt update
> > -RUN apt install -yy build-essential clang
> > +# Setup Emdebian
> > +RUN echo "deb http://emdebian.org/tools/debian/ jessie main" >> /etc/apt/sources.list 
> > && \
> > +    curl http://emdebian.org/tools/debian/emdebian-toolchain-archive.key | 
> > apt-key add -
>
> Why move this to the end? Once we have curl installed it would be nice
> to do just one update step and have emdebian synced up in the base
> image.

In the first apt-get can install curl + build-essential clang in the 
same call, and there is no need to fetch emdebian.org index.

Using 'apt clean' at the end of a layer keeps smaller layer but the next 
layer have to call `apt-get update` again. Since this base image is used 
to cross-compile, the child image will have to call `dpkg 
--add-architecture ...` before fetching emdebian.org arch index again 
(apt-get update) to be able to install the `crossbuild-essential-$arch` 
package.
So there is no need to update right after adding this repo, the 'child' 
will do it (and have to do it).

> --
> Alex Bennée