Where are the packages installed with `apt-get install` in Docker containers?
<p>I'm trying to locate the <code>libgsl.so</code> library in a Docker container after installing it successfully . </p>

<p>When I run an interactive shell with <code>docker run -it container/image bash</code> and try to find it <code>find / -iname "*libgsl*"</code> I get nothing (the tool tries to find it under /usr/lib/). It seems that the same is true for another successfully installed libraries (e.g. libjpeg62).</p>

<p>So, generally, <strong>where are these libraries being installed</strong>?</p>

<p>I'm running Docker with VBox in MacOS. 
Here is the <code>Dockerfile</code> file:</p>

<pre><code>FROM phusion/baseimage

# Install dependencies
RUN apt-get update &amp;&amp; apt-get install -y \
  libgsl0ldbl \
  curl \
  gsl-bin

# Installs preseq from sources into /opt/
ENV PRESEQ_RELEASE=2.0
ENV PRESEQ_URL=http://smithlabresearch.org/downloads/preseq_linux_v${PRESEQ_RELEASE}.tar.bz2
ENV DEST_DIR=/opt/

# Download preseq; untar &amp; decompress; remove tr.bz2 file; compile &amp; install preseq; remove unnecessary files
RUN curl -SLo ${DEST_DIR}/preseq_v${PRESEQ_RELEASE}.tar.bz2 ${PRESEQ_URL} &amp;&amp; \
  tar -xf ${DEST_DIR}/preseq_v${PRESEQ_RELEASE}.tar.bz2 -C ${DEST_DIR} &amp;&amp; \
  rm -f ${DEST_DIR}/preseq_v${PRESEQ_RELEASE}.tar.bz2

ENV PATH=${DEST_DIR}/preseq_v${PRESEQ_RELEASE}:$PATH
CMD ["preseq"]
</code></pre>

<hr>

<p><strong>UPDATE</strong></p>

<p>I was running the wrong container (not using the right tag) where I didn't have the library installed. After changing the tag, I found the libraries without a problem. Packages are installed in the default locations (in this case /usr/lib/).</p>