[Dockerfile] Some of the little skills used in Dockerfile

I collect some of the little skills used in my Dockerfiles and also keep in the record for my reference.

--build-arg & ARG
you can pass your parameter via --build-arg in your docker build command and use ARG to receive the value in Dockerfile. For instance:

<<Your Dockerfile>>
FROM tensorflow/tensorflow:latest-gpu

ARG MCUT_USER  # get parameter value from docker build --build-arg=XXXX
...
...
...

$ sudo docker build --build-arg UBUNTU_USER=danny -t my_image:v0 .

Use wget to download a directory

<<Your Dockerfile>>
...
ARG MODEL1_LINK=https://download.01.org/opencv/2019/open_model_zoo/R1/models_bin_20190329_105530/pedestrian-detection-adas-0002/

# Download OpenVINO pre-trained models
RUN wget -r -np -nH --cut-dirs=5 -R index.html* $MODEL1_LINK
...

ENTRYPOINT and CMD instruction

<<Your Dockerfile>>
...
ENTRYPOINT ["fixuid"]
CMD ["bash", "/startup.sh"]
# which means ==> "fixuid bash /startup.sh"

USER instruction

USER <user>[:<group>] or
USER <UID>[:<GID>]

<<Your Dockerfile>>
...
# Add user & group ==> danny:danny
RUN groupadd -r danny && \
useradd -d /workspace -r -g danny danny && \
usermod -s /bin/bash danny

# or add user & group id
RUN addgroup --gid 1000 docker && \
    adduser --uid 1000 --ingroup danny && \
            --home /workspace --shell /bin/bash && \
            --disabled-password --gecos "" danny

USER danny:danny

Multi-Stage-Build
https://docs.docker.com/engine/userguide/eng-image/multistage-build/#use-multi-stage-builds

<<Your Dockerfile>>
...
FROM gcr.io/kaggle-images/python-tensorflow-whl:1.13.1-py36-2 as tensorflow_whl
...
COPY --from=tensorflow_whl /tmp/tensorflow_gpu/*.whl /tmp/tensorflow_gpu/
...

P.S: COPY --from=0 ==> means to use the previous build's result

Reference:

Alpine Linux で Docker イメージを劇的に小さくする

Example:

alpine-nginx.dockerfile

FROM alpine:3.4

ENV NGINX_VERSION 1.11.1

RUN apk --update add pcre-dev openssl-dev \
  && apk add --virtual build-dependencies build-base curl \
  && curl -SLO http://nginx.org/download/nginx-${NGINX_VERSION}.tar.gz \
  && tar xzvf nginx-${NGINX_VERSION}.tar.gz \
  && cd nginx-${NGINX_VERSION} \
  && ./configure \
       --with-http_ssl_module \
       --with-http_gzip_static_module \
       --prefix=/usr/share/nginx \
       --sbin-path=/usr/local/sbin/nginx \
       --conf-path=/etc/nginx/conf/nginx.conf \
       --pid-path=/var/run/nginx.pid \
       --http-log-path=/var/log/nginx/access.log \
       --error-log-path=/var/log/nginx/error.log \
  && make \
  && make install \
  && ln -sf /dev/stdout /var/log/nginx/access.log \
  && ln -sf /dev/stderr /var/log/nginx/error.log \
  && cd / \
  && apk del build-dependencies \
  && rm -rf \
       nginx-${NGINX_VERSION} \
       nginx-${NGINX_VERSION}.tar.gz \
       /var/cache/apk/*

VOLUME ["/var/cache/nginx"]

EXPOSE 80 443

CMD ["nginx", "-g", "daemon off;"]

Alpine Linux で軽量な Docker イメージを作る

apk --update add什麼時候apk --no-cache add

Alpine Linux 從 3.3 開始有一個帶有 apk 的選項--no-cache。
以前--update add用with安裝後好像rm -rf /var/cache/apk/*會
刪除不必要的垃圾文件，現在--no-cache可以了。

apk add --virtual用於

--virtual您可以通過指定apk 來安裝軟件包，
但如果您使用此選項使用臨時名稱進行安裝，您
可以稍後使用臨時名稱一次性刪除它們。

- 虛擬的

RUN apk add --no-cache --virtual .ruby-builddeps curl gcc make .. && \
    curl ... && \
    ... && \
    make install ... && \
    apk del .ruby-builddeps

這樣可以防止被刪除，非常方便！