title: Docker: COPY failed: stat <file>: file does not exist
body: <p>I am trying to copy a file into my docker container but the command fails. The file is in the same directory as the Dockerfile, so I don't understand the reason for the error.</p>
  <p>I'd appreciate any help or advice. Thanks beforehand.</p>
  <p>This is the code:</p>
  <pre><code>FROM ubuntu:20.04 as builder
  ENV DEBIAN_FRONTEND=noninteractive 
  
  RUN apt-get update
  RUN apt-get install -y \
      build-essential \
      cmake \
      software-properties-common \
      libopencv-dev
  
  RUN add-apt-repository -y ppa:chrberger/libcluon
  RUN apt-get update
  RUN apt-get install -y libcluon
  
  ADD . /opt/sources
  WORKDIR /opt/sources
  RUN mkdir build &amp;&amp; \
      cd build &amp;&amp; \
      cmake -D CMAKE_BUILD_TYPE=Release -D CMAKE_INSTALL_PREFIX=/tmp/dest .. &amp;&amp; \
      make &amp;&amp; make install
  
  
  FROM ubuntu:20.04
  ENV DEBIAN_FRONTEND=noninteractive 
  
  RUN apt-get update --fix-missing
  RUN apt-get install -y \
      libopencv-core4.2 \
      libopencv-imgproc4.2 \
      libopencv-video4.2 \
      libopencv-calib3d4.2 \
      libopencv-features2d4.2 \
      libopencv-objdetect4.2 \
      libopencv-highgui4.2 \
      libopencv-videoio4.2 \
      libopencv-flann4.2 \
      libopencv-dnn-dev \
      python3-opencv
  
  WORKDIR /usr/bin
  COPY --from=builder /tmp/dest /usr
  COPY --from=builder yolov3-tiny_obj.cfg /params
  ENTRYPOINT [&quot;/usr/bin/opendlv-perception-helloworld&quot;]
  </code></pre>