Dockerfile and including other repositories for use with apt-get - docker

Question

Whilst the particular base linux docker image we use currently escapes me, the problem I have is I need to include the Postgresql Client.
apt-get update allowed me to install it, but I discovered it was only version 9, and I needed 10 to match my Postgres DB.
If the docker is running and I used exec bash to access it I can run the following commands to install version 10...
echo "deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main" >> /etc/apt/sources.list.d/pgdg.list
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add -
apt-get update
apt-get -y install postgresql-client-10
So I then set about adding these to my Dockerfile so it would be included automatically, the result being...
RUN echo "deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main" >> /etc/apt/sources.list.d/pgdg.list
RUN wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add -
RUN apt-get update
RUN apt-get -y install postgresql-client-10
When Visual Studio (Mac 2019) builds the docker, it completely ignores this. When I built it from the command line, the output suggested it had done as it should, what Docker Cloud builds it I get the error...
Step 17/24 : COPY --from=publish /app .
---> 091e71bd17c0
Step 18/24 : RUN echo "deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main" >> /etc/apt/sources.list.d/pgdg.list
---> Running in 8582e2dba910
/bin/sh: can't create /etc/apt/sources.list.d/pgdg.list: nonexistent directory
Removing intermediate container 8582e2dba910
The command '/bin/sh -c echo "deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main" >> /etc/apt/sources.list.d/pgdg.list' returned a non-zero code: 1
Note the 3rd line up about can't create pgdg.list
So how should I go about doing this?

Answer 1

Your approach with the additional Dockerfile statements is sound. However, it's unclear how you're extending your previous container image to include these.
Usually you'd have something of the form:
FROM my-original-image:its-version
RUN ...
RUN ...
RUN apt-get update
RUN apt-get -y install postgresql-client-10
This approach would add postgresql-client-10 to whatever's installed in my-original-image:its-version.
An alternative approach is to start from the base from which my-original-image:its-version uses and install postgresql-client-10 instead of the previous version. Your choice.
If my-original-image were created using:
FROM some-base
RUN apt update && apt install -y postgresql-client-9
You could:
FROM some-base
RUN apt update && apt install -y postgresql-client-10
NB You'd have to duplicate the installation of other dependencies too.
Update
See instructions for Dockerizing Postgres here. The Postgres PGP key has possibly been dropped from your image and is causing errors.
FROM debian:stretch-slim
RUN apt-get update && apt-get install -y \
gnupg2 \
wget \
&& apt-key adv \
--keyserver hkp://p80.pool.sks-keyservers.net:80 \
--recv-keys B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8 \
&& echo "deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main" \
>> /etc/apt/sources.list.d/pgdg.list \
&& wget \
--quiet \
--output-document - \
https://www.postgresql.org/media/keys/ACCC4CF8.asc \
| apt-key add - \
&& apt-get update \
&& apt-get install -y \
postgresql-client-10 \
&& rm -rf /var/lib/apt/lists/*