A Dockerfile that installs conda. Uses a GPU-enabled image (with CUDA) as a base, but miniconda install & setup is portable.

conda.Dockerfile

# syntax=docker/dockerfile:1.3
ARG UBUNTU_VERSION=18.04
ARG CUDA_VERSION=11.3.1

# Or use a different image. 
FROM nvidia/cuda:${CUDA_VERSION}-cudnn8-devel-ubuntu${UBUNTU_VERSION}

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#                                                                 #
#                         system packages                         #
#            (ensure python & shared libs are present!)           #
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RUN apt --allow-releaseinfo-change update -q && \
    apt-get install -q -y \
    bzip2 \
    ca-certificates \
    git \
    libgl1 \
    libglib2.0-0 \
    libsm6 \
    libxext6 \
    libxrender1 
    wget \
    nginx \
    libcurl4-openssl-dev \
    libssl-dev \
    python3-dev \
    gcc \
    && apt-get clean


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#                                                                 #
#                         install conda                           #
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# Miniconda
# https://github.com/ContinuumIO/docker-images/blob/4ed8fdac4647e4cc4210f84a327c3b7c92802b5d/miniconda3/debian/Dockerfile

ENV PATH /opt/conda/bin:$PATH

# Leave these args here to better use the Docker build cache
ARG CONDA_VERSION=py38_4.9.2
ARG CONDA_MD5=122c8c9beb51e124ab32a0fa6426c656

RUN wget --quiet https://repo.anaconda.com/miniconda/Miniconda3-${CONDA_VERSION}-Linux-x86_64.sh -O miniconda.sh && \
    echo "${CONDA_MD5}  miniconda.sh" > miniconda.md5 && \
    if ! md5sum --status -c miniconda.md5; then exit 1; fi && \
    mkdir -p /opt && \
    sh miniconda.sh -b -p /opt/conda && \
    rm miniconda.sh miniconda.md5 && \
    ln -s /opt/conda/etc/profile.d/conda.sh /etc/profile.d/conda.sh && \
    echo ". /opt/conda/etc/profile.d/conda.sh" >> ~/.bashrc && \
    echo "conda activate base" >> ~/.bashrc && \
    find /opt/conda/ -follow -type f -name '*.a' -delete && \
    find /opt/conda/ -follow -type f -name '*.js.map' -delete && \
    /opt/conda/bin/conda clean -afy

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#                                                                 #
#               can now use `conda` in RUN steps                  #
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