The preconfigured environments available through the Terra interface are regularly updated. In this article, you'll learn about several options for selecting prior versions of containers, and tracking updates to the preconfigured ones.
Cloud Environments basics
Cloud Environments are packaged in a Docker container, a unit of software that contains instructions for installing all the libraries, packages, and dependencies needed for a given application to run smoothly.
Dockers keep track of all software dependencies
Typically, a Docker container contains a long list of interdependent code packages, which can be challenging to remember. But because Terra takes care of versioning the contents, you only need to know the version of the Docker image you’re using (and any packages you install manually).
You can always select the latest (default) environment in Terra when configuring your Cloud Environment.
When you might need a legacy Docker container
Incorrect versions of any of the packages in the container you’re using can break your code.
If you've been working in the same notebook for a month or longer, the default Docker has likely changed. If your notebook was written and tested in a default environment, your notebook may not function as expected if the default environment has been updated and your Cloud Environment is using an updated default.
In that case, you may need to either update your code or select a legacy environment.
Ensure you're running the right versions of each package
1. To check if you need an older version of a container, select one of the legacy configurations in the environment drop-down menu and check the date at which a given configuration was frozen in a “legacy state”.
If the default has been updated since you ran your analysis, you may need to use a legacy environment to reproduce prior results. 
What to expect
Using the right version of GATK or your programming language of choice may address all of your issues.
Additional information
The label also includes additional information about which version of GATK, R, and Python is part of that pre-configured environment.
If using a legacy Docker doesn't solve your problems
2. You can visit our Git for more detail about the individual package versions in each preconfigured environment.
Here you can check exactly what packages are present in each of our base images, to compare.
Custom Docker
The Git is where you go to download the base images so you can modify them to create your own custom docker image (check out this tutorial).
Additional Resources
Previous Docker images in the Broad Container Registry
- You can find all previous Terra Docker images in the Broad Google Container Registry. See this guide to get started!
Stay up to date on preset cloud configurations
- Finally, you can follow our release notes to stay informed about updates to our preset cloud environment configurations.