Add conda installation instructions (#870)

(cherry picked from commit 890aac6)

Author: vishalbollu

docs/deployments/python-packages.md

@@ -85,3 +85,46 @@ git+https://<personal access token>@github.com/<username>/<repo name>.git@<tag o
 ```
 
 You can generate a personal access token by following [these steps](https://help.github.com/en/github/authenticating-to-github/creating-a-personal-access-token-for-the-command-line).
+
+## Conda packages
+
+You can install Conda packages by creating a custom Docker image that first installs Conda and then installs your Conda packages.
+
+Customize the template Dockerfile below with your desired Conda packages and follow these [instructions](./system-packages.md) to build and push your image to a container registry and configure Cortex to use your custom image.
+
+```dockerfile
+# Dockerfile
+
+FROM <BASE CORTEX IMAGE>
+
+# remove system-wide packages from the base image
+RUN pip freeze > req && for pkg in "$(cat req)"; do pip uninstall $pkg -y || true; done && rm req
+
+# add conda to path
+ENV PATH /opt/conda/bin:$PATH
+
+# install conda, it also includes py3.6.9
+RUN curl https://repo.anaconda.com/miniconda/Miniconda3-4.7.12.1-Linux-x86_64.sh --output ~/miniconda.sh && \
+    /bin/bash ~/miniconda.sh -b -p /opt/conda && \
+    rm ~/miniconda.sh && \
+    /opt/conda/bin/conda update conda && \
+    /opt/conda/bin/conda install --force python=3.6.9 && \
+    /opt/conda/bin/conda clean -tipsy && \
+    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
+
+# install pip dependencies
+RUN pip install --upgrade pip && \
+    pip install --no-cache-dir -r /src/cortex/lib/requirements.txt && \
+    pip install --no-cache-dir -r /src/cortex/serve/requirements.txt
+
+# ---------------------------------------------------------- #
+# Install your Conda packages here
+# RUN conda install --no-update-deps -c conda-forge rdkit
+
+# ---------------------------------------------------------- #
+
+# replace system python with conda's version
+RUN sed -i 's/\/usr\/bin\/python3.6/\/opt\/conda\/bin\/python/g' /src/cortex/serve/run.sh
+```

docs/deployments/system-packages.md

@@ -12,6 +12,8 @@ mkdir my-api && cd my-api && touch Dockerfile
 
 The Docker images used to deploy your models are listed below. Based on the Cortex Predictor and compute type specified in your API configuration, choose a Cortex image to use as the base for your custom Docker image.
 
+### Base Cortex images
+
 <!-- CORTEX_VERSION_BRANCH_STABLE x5 -->
 * Python (CPU): cortexlabs/python-serve:0.14.1
 * Python (GPU): cortexlabs/python-serve-gpu:0.14.1