---
layout: default
navsection: sdk
navmenu: Python
title: Arvados CWL Runner
...
{% comment %}
Copyright (C) The Arvados Authors. All rights reserved.

SPDX-License-Identifier: CC-BY-SA-3.0
{% endcomment %}

The Arvados CWL Runner is a Python tool that allows you to register and submit workflows to Arvados. You can oversee a running workflow on your local system, or let that run inside an Arvados container. This tool requires the Python SDK installed in order to access Arvados services.

h2. Installation

If you are logged in to a managed Arvados VM, the @arvados-cwl-runner@ utility should already be installed.

To use the CWL Runner elsewhere, you can install it from a distribution package or PyPI.

h2. Option 1: Install from distribution packages

First, "add the appropriate package repository for your distribution":{{ site.baseurl }}/install/packages.html.

{% assign arvados_component = 'python3-arvados-cwl-runner' %}

{% include 'install_packages' %}

h2. Option 2: Install with pip

Run @pip install arvados-cwl-runner@ in an appropriate installation environment, such as a virtualenv.

Note:

The CWL Runner uses @pycurl@ which depends on the @libcurl@ C library.  To build the module you may have to first install additional packages.  On Debian-based distributions you can install them by running:

<notextile>
<pre><code># <span class="userinput">apt install git build-essential python3-dev libcurl4-openssl-dev libssl-dev</span>
</code></pre>
</notextile>

h2. Check Docker access

In order to pull and upload Docker images, @arvados-cwl-runner@ requires access to Docker.  You do not need Docker if the Docker images you intend to use are already available in Arvados.

You can determine if you have access to Docker by running @docker version@:

<notextile>
<pre><code>~$ <span class="userinput">docker version</span>
Client:
 Version:      1.9.1
 API version:  1.21
 Go version:   go1.4.2
 Git commit:   a34a1d5
 Built:        Fri Nov 20 12:59:02 UTC 2015
 OS/Arch:      linux/amd64

Server:
 Version:      1.9.1
 API version:  1.21
 Go version:   go1.4.2
 Git commit:   a34a1d5
 Built:        Fri Nov 20 12:59:02 UTC 2015
 OS/Arch:      linux/amd64
</code></pre>
</notextile>

If this returns an error, contact the sysadmin of your cluster for assistance.

h2. Usage

Please refer to the "Starting a Workflow at the Command Line":{{site.baseurl}}/user/cwl/cwl-runner.html tutorial for more information.