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When your base image is hosted on a private registry, you need to provide authentication credentials so fal can pull the image during container builds. This page covers the setup for Docker Hub, Google Artifact Registry, and Amazon ECR, including how to manage tokens securely using fal’s secrets management. These credentials are passed via the registries parameter on ContainerImage. Each registry uses a different authentication method, so follow the section below that matches your registry provider.

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Dockerhub

class MyModel(fal.App):
    image = fal.container.ContainerImage.from_dockerfile_str(
        "FROM myuser/image:tag",
        registries={
            "https://index.docker.io/v1/": {
                "username": "myuser",
                "password": "$DOCKERHUB_TOKEN",  # Use `fal secrets set` to create this secret
            },
        },
    )

​
Google Artifact Registry

We recommend using a service account and setting a base64-encoded version of the key as a fal secret.
1

Create a JSON key for a service account.

Download the key file to your local machine.
2

Encode the key in base64.

cat key.json | base64
3

Set the result as a fal secret.

fal secrets set GOOGLE_AR_JSON_BASE64=<base64-value>
4

Use the secret in your code.

class MyModel(fal.App):
    image = fal.container.ContainerImage.from_dockerfile_str(
        "FROM us-central1-docker.pkg.dev/my-project/my-repo/image:tag",
        registries={
            "us-central1-docker.pkg.dev": {
                "username": "_json_key_base64",
                "password": "$GOOGLE_AR_JSON_BASE64",
            },
        },
    )

​
Amazon Elastic Container Registry (ECR)

ECR tokens expire every 12 hours. It’s best to auto-generate one on the fly using boto3 and your AWS credentials. 
import os
import boto3
import base64

def get_ecr_token(region: str) -> str:
    ecr_client = boto3.client(
        'ecr',
        aws_access_key_id=os.environ["AWS_ACCESS_KEY_ID"],
        aws_secret_access_key=os.environ["AWS_SECRET_ACCESS_KEY"],
        region_name=region
    )
    response = ecr_client.get_authorization_token()
    auth_data = response['authorizationData'][0]
    token = auth_data['authorizationToken']
    # Decode from base64, format is "AWS:password"
    decoded_token = base64.b64decode(token).decode('utf-8')
    _, password = decoded_token.split(':', 1)
    return password

class MyModel(fal.App):
    image = fal.container.ContainerImage.from_dockerfile_str(
        "FROM 123456789012.dkr.ecr.us-east-1.amazonaws.com/image:tag",
        registries={
            "123456789012.dkr.ecr.us-east-1.amazonaws.com": {
                "username": "AWS",
                "password": get_ecr_token("us-east-1"),
            },
        },
    )