Where is the Postgres username/password being created in this Dockerfile?

Question

So I was following this tutorial: https://realpython.com/blog/python/django-development-with-docker-compose-and-machine/

I have everything up and running, however theres a few things going on that I'm not able to follow or understand.

In the main Docker-Compose we have:

web:
  restart: always
  build: ./web
  expose:
    - "8000"
  links:
    - postgres:postgres
    - redis:redis
  volumes:
    - /usr/src/app
    - /usr/src/app/static
  env_file: .env
  command: /usr/local/bin/gunicorn docker_django.wsgi:application -w 2 -b :8000

postgres:
  restart: always
  image: postgres:latest
  ports:
    - "5432:5432"
  volumes:
    - pgdata:/var/lib/postgresql/data/

You will notice there is a env_file containing:

DB_NAME=postgres    
DB_USER=postgres    
DB_PASS=postgres

我的问题是何时设置postgres用户和密码？如果我运行此docker-compose，则一切正常，这意味着Web应用程序可以将凭据传递到postgress数据库并建立连接。但是，我无法遵循这些信息，这些信息是首先设置的。

我假设在基本的postgres Dockerfile中，会有一些指令来设置数据库名称，用户名和密码。我不知道。这是下面的基本postgres Dockerfile的副本。

# vim:set ft=dockerfile:

FROM debian:jessie



# explicitly set user/group IDs

RUN groupadd -r postgres --gid=999 && useradd -r -g postgres --uid=999 postgres



# grab gosu for easy step-down from root

ENV GOSU_VERSION 1.7

RUN set -x \

    && apt-get update && apt-get install -y --no-install-recommends ca-certificates wget && rm -rf /var/lib/apt/lists/* \

    && wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$(dpkg --print-architecture)" \

    && wget -O /usr/local/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$(dpkg --print-architecture).asc" \

    && export GNUPGHOME="$(mktemp -d)" \

    && gpg --keyserver ha.pool.sks-keyservers.net --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4 \

    && gpg --batch --verify /usr/local/bin/gosu.asc /usr/local/bin/gosu \

    && rm -r "$GNUPGHOME" /usr/local/bin/gosu.asc \

    && chmod +x /usr/local/bin/gosu \

    && gosu nobody true \

    && apt-get purge -y --auto-remove ca-certificates wget



# make the "en_US.UTF-8" locale so postgres will be utf-8 enabled by default

RUN apt-get update && apt-get install -y locales && rm -rf /var/lib/apt/lists/* \

    && localedef -i en_US -c -f UTF-8 -A /usr/share/locale/locale.alias en_US.UTF-8

ENV LANG en_US.utf8



RUN mkdir /docker-entrypoint-initdb.d



RUN apt-key adv --keyserver ha.pool.sks-keyservers.net --recv-keys B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8



ENV PG_MAJOR 9.6

ENV PG_VERSION 9.6.1-1.pgdg80+1



RUN echo 'deb http://apt.postgresql.org/pub/repos/apt/ jessie-pgdg main' $PG_MAJOR > /etc/apt/sources.list.d/pgdg.list



RUN apt-get update \

    && apt-get install -y postgresql-common \

    && sed -ri 's/#(create_main_cluster) .*$/\1 = false/' /etc/postgresql-common/createcluster.conf \

    && apt-get install -y \

        postgresql-$PG_MAJOR=$PG_VERSION \

        postgresql-contrib-$PG_MAJOR=$PG_VERSION \

    && rm -rf /var/lib/apt/lists/*



# make the sample config easier to munge (and "correct by default")

RUN mv -v /usr/share/postgresql/$PG_MAJOR/postgresql.conf.sample /usr/share/postgresql/ \

    && ln -sv ../postgresql.conf.sample /usr/share/postgresql/$PG_MAJOR/ \

    && sed -ri "s!^#?(listen_addresses)\s*=\s*\S+.*!\1 = '*'!" /usr/share/postgresql/postgresql.conf.sample



RUN mkdir -p /var/run/postgresql && chown -R postgres /var/run/postgresql



ENV PATH /usr/lib/postgresql/$PG_MAJOR/bin:$PATH

ENV PGDATA /var/lib/postgresql/data

VOLUME /var/lib/postgresql/data



COPY docker-entrypoint.sh /



ENTRYPOINT ["/docker-entrypoint.sh"]



EXPOSE 5432

CMD ["postgres"]

Answer 1

不确定您使用的是哪个 postgres 图像。

如果您查看官方 postgres 图像以获取完整信息。它允许用户为以下环境变量指定环境变量，这些可以在运行时轻松覆盖。

• POSTGRES_PASSWORD
• POSTGRES_USER
• 数据
• POSTGRES_DB
• POSTGRES_INITDB_ARGS

根据您的情况，可以使用以下三种方法覆盖环境变量。

• 运行镜像：如果直接运行 docker 镜像，请使用下面的方式在docker runwith 中包含环境变量-e K=V。请在此处参阅文档以获取更多详细信息

docker run -e POSTGRES_PASSWORD=secrect -e POSTGRES_USER=postgres <other options> image/name

• Dockerfile：如果需要在 中指定环境变量Dockerfile，请按如下方式指定。请在此处参阅文档以获取更多详细信息

ENV POSTGRES_PASSWORD=secrect
ENV POSTGRES_USER=postgres

• docker-compose：如果需要在 中指定环境变量docker-compose.yml，请指定如下。请在此处参阅文档以获取更多详细信息

web:
  environment:
    - POSTGRES_PASSWORD=secrect
    - POSTGRES_USER=postgres

希望这是有用的。

Answer 2

我认为 postgres 用户和密码是在入口点设置的，就像在官方图像入口点的第 23 行一样。

https://github.com/docker-library/postgres/blob/e4942cb0f79b61024963dc0ac196375b26fa60dd/9.6/docker-entrypoint.sh

你能检查你的入口点吗？