Note: This is not an official Google product.
This is a Docker image used by the CoreOS Toolbox script on Container-Optimized OS. This image comes pre-installed with common debugging tools that are not pre-installed on the host.
The official toolbox container is available at gcr.io/google-containers/toolbox.
Current tag: 20161110-02
For detailed documentation on how this is used, see https://cloud.google.com/container-optimized-os/docs/how-to/toolbox.