Custom Sandbox

The sandbox is where the agent performs its tasks. Instead of running commands directly on your computer (which could be risky), the agent runs them inside a Docker container.

The default OpenHands sandbox (python-nodejs:python3.12-nodejs22 from nikolaik/python-nodejs) comes with some packages installed such as python and Node.js but may need other software installed by default.

You have two options for customization:

Use an existing image with the required software.
Create your own custom Docker image.

If you choose the first option, you can skip the Create Your Docker Image section.

Create Your Docker Image

To create a custom Docker image, it must be Debian based.

For example, if you want OpenHands to have ruby installed, create a Dockerfile with the following content:

FROM debian:latest

# Install required packages
RUN apt-get update && apt-get install -y ruby

Save this file in a folder. Then, build your Docker image (e.g., named custom-image) by navigating to the folder in the terminal and running::

docker build -t custom-image .

This will produce a new image called custom-image, which will be available in Docker.

Note that in the configuration described in this document, OpenHands will run as user "openhands" inside the sandbox and thus all packages installed via the docker file should be available to all users on the system, not just root.

Using the Development Workflow

Setup

First, ensure you can run OpenHands by following the instructions in Development.md.

Specify the Base Sandbox Image

In the config.toml file within the OpenHands directory, set the sandbox_base_container_image to the image you want to use. This can be an image you’ve already pulled or one you’ve built:

[core]
...
sandbox_base_container_image="custom-image"

Run

Run OpenHands by running make run in the top level directory.

Technical Explanation

Please refer to custom docker image section of the runtime documentation for more details.

Troubleshooting / Errors

Error: `useradd: UID 1000 is not unique`

If you see this error in the console output it is because OpenHands is trying to create the openhands user in the sandbox with a UID of 1000, however this UID is already being used in the image (for some reason). To fix this change the sandbox_user_id field in the config.toml file to a different value:

[core]
workspace_base="./workspace"
run_as_openhands=true
sandbox_base_container_image="custom_image"
sandbox_user_id="1001"

Port use errors

If you see an error about a port being in use or unavailable, try deleting all running Docker Containers (run docker ps and docker rm relevant containers) and then re-running make run .

Discuss

For other issues or questions join the Slack or Discord and ask!

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