# Setup

## Requirements

To go through this tutorial, you need the following software installed:

- Python ≥3.5

- Snakemake ≥5.24.1

- BWA 0.7

- SAMtools 1.9

- Pysam 0.15

- BCFtools 1.9

- Graphviz 2.42

- Jinja2 2.11

- NetworkX 2.5

- Matplotlib 3.3

However, don’t install any of these this manually now, we guide you through better ways below.

## Run tutorial for free in the cloud via Gitpod

The easiest way to run this tutorial is to use Gitpod, which enables performing the excercises via your browser—including all required software, for free and in the cloud. In order to do this, simply open the predefined snakemake-tutorial GitPod workspace in your browser. GitPod provides you with a Theia development environment, which you can learn about in the linked documentation. Once you have a basic understanding of this environment, you can go on directy with Basics: An example workflow.

## Running the tutorial on your local machine

If you prefer to run the tutorial on your local machine, please follow the steps below.

The easiest way to set these prerequisites up, is to use the Mambaforge Python 3 distribution (Mambaforge is a Conda based distribution like Miniconda, which however uses Mamba a fast and more robust replacement for the Conda package manager). The tutorial assumes that you are using either Linux or MacOS X. Both Snakemake and Mambaforge work also under Windows, but the Windows shell is too different to be able to provide generic examples.

## Setup on Windows

If you already use Linux or MacOS X, go on with Step 1.

### Windows Subsystem for Linux

If you use Windows 10, you can set up the Windows Subsystem for Linux (WSL) to natively run linux applications. Install the WSL following the instructions in the WSL Documentation. You can chose any Linux distribution available for the WSL, but the most popular and accessible one is Ubuntu. Start the WSL and set up your account; now, you can follow the steps of our tutorial from within your Linux environment in the WSL.

### Vagrant virtual machine

If you are using a version of Windows older than 10 or if you do not wish to install the WSL, you can instead setup a Linux virtual machine (VM) with Vagrant. First, install Vagrant following the installation instructions in the Vagrant Documentation. Then, create a new directory you want to share with your Linux VM, for example, create a folder named `vagrant-linux` somewhere. Open a command line prompt, and change into that directory. Here, you create a 64-bit Ubuntu Linux environment with

    > vagrant init hashicorp/precise64
    > vagrant up

If you decide to use a 32-bit image, you will need to download the 32-bit version of Miniconda in the next step. The contents of the `vagrant-linux` folder will be shared with the virtual machine that is set up by vagrant. You can log into the virtual machine via

    > vagrant ssh

If this command tells you to install an SSH client, you can follow the instructions in this Blogpost. Now, you can follow the steps of our tutorial from within your Linux VM.

## Step 1: Installing Mambaforge

First, please open a terminal or make sure you are logged into your Vagrant Linux VM. Assuming that you have a 64-bit system, on Linux, download and install Miniconda 3 with

    $ curl -L https://github.com/conda-forge/miniforge/releases/latest/download/Mambaforge-Linux-x86_64.sh -o Mambaforge-Linux-x86_64.sh
    $ bash Mambaforge-Linux-x86_64.sh

On MacOS with x86_64 architecture, download and install with

    $ curl -L https://github.com/conda-forge/miniforge/releases/latest/download/Mambaforge-MacOSX-x86_64.sh -o Mambaforge-MacOSX-x86_64.sh
    $ bash Mambaforge-MacOSX-x86_64.sh

On MacOS with ARM/M1 architecture, download and install with

    $ curl -L https://github.com/conda-forge/miniforge/releases/latest/download/Mambaforge-MacOSX-arm64.sh -o Mambaforge-MacOSX-arm64.sh
    $ bash Mambaforge-MacOSX-arm64.sh

When you are asked the question

    Do you wish the installer to prepend the install location to PATH ...? [yes|no]

answer with yes. Along with a minimal Python 3 environment, Mambaforge contains the package manager Mamba. After closing your current terminal and opening a new terminal, you can use the new `conda` command to install software packages and create isolated environments to, for example, use different versions of the same package. We will later use Conda to create an isolated environment with all the required software for this tutorial.

## Step 2: Preparing a working directory

First, create a new directory `snakemake-tutorial` at a place you can easily remember and change into that directory in your terminal:

    $ mkdir snakemake-tutorial
    $ cd snakemake-tutorial

If you use a Vagrant Linux VM from Windows as described above, create that directory under `/vagrant/`, so that the contents are shared with your host system (you can then edit all files from within Windows with an editor that supports Unix line breaks). Then, change to the newly created directory. In this directory, we will later create an example workflow that illustrates the Snakemake syntax and execution environment. First, we download some example data on which the workflow shall be executed:

    $ curl -L https://api.github.com/repos/snakemake/snakemake-tutorial-data/tarball -o snakemake-tutorial-data.tar.gz

Next we extract the data. On Linux, run

    $ tar --wildcards -xf snakemake-tutorial-data.tar.gz --strip 1 "*/data" "*/environment.yaml"

On MacOS, run

    $ tar -xf snakemake-tutorial-data.tar.gz --strip 1 "*/data" "*/environment.yaml"

This will create a folder `data` and a file `environment.yaml` in the working directory.

## Step 3: Creating an environment with the required software

First, make sure to activate the conda base environment with

    $ conda activate base

The `environment.yaml` file that you have obtained with the previous step (Step 2) can be used to install all required software into an isolated Conda environment with the name `snakemake-tutorial` via

    $ mamba env create --name snakemake-tutorial --file environment.yaml

If you don’t have the Mamba command because you used a different conda distribution than Mambaforge, you can also first install Mamba (which is a faster and more robust replacement for Conda) in your base environment with

    $ conda install -n base -c conda-forge mamba

and then run the mamba env create command shown above.

## Step 4: Activating the environment

To activate the `snakemake-tutorial` environment, execute

    $ conda activate snakemake-tutorial

Now you can use the installed tools. Execute

    $ snakemake --help

to test this and get information about the command-line interface of Snakemake. To exit the environment, you can execute

    $ conda deactivate

but don’t do that now, since we finally want to start working with Snakemake :-).