---
layout: default
navsection: userguide
title: "Customizing the Crunch runtime environment"
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This page describes how to customize the runtime environment (e.g. the programs, libraries, and other dependencies needed to run a job) that a crunch script will be run in.

{% include 'tutorial_expectations' %}

h1. Docker

Arvados uses "Docker":https://www.docker.com/ images to provide a runtime environment for Crunch jobs.

This page will demonstrate how to build the arvados/jobs Docker image, manually install additional software into the image to create a new custom image, and upload that image to Arvados for use by Crunch jobs.

Arvados images are based on "Debian.":https://debian.org  In order to build

cd ~/arvados/docker
./build.sh jobs-image