# modal.CloudBucketMount | Modal Docs

- **URL:** https://modal.com/docs/sdk/py/latest/modal.CloudBucketMount
- **Summary:** Mounts a cloud bucket to your container. Currently supports AWS S3 buckets.

Copy page

modal.CloudBucketMount
======================

    class CloudBucketMount(object)

Mounts a cloud bucket to your container. Currently supports AWS S3 buckets.

S3 buckets are mounted using [AWS S3 Mountpoint](https://github.com/awslabs/mountpoint-s3)
. S3 mounts are optimized for reading large files sequentially. It does not support every file operation; consult [the AWS S3 Mountpoint documentation](https://github.com/awslabs/mountpoint-s3/blob/main/doc/SEMANTICS.md)
 for more information.

**Usage**

S3:

    import subprocess
    
    app = modal.App()
    secret = modal.Secret.from_name(
        "aws-secret",
        required_keys=["AWS_ACCESS_KEY_ID", "AWS_SECRET_ACCESS_KEY"]
        # Note: providing AWS_REGION can help when automatic detection of the bucket region fails.
    )
    
    @app.function(
        volumes={
            "/my-mount": modal.CloudBucketMount(
                bucket_name="s3-bucket-name",
                secret=secret,
                read_only=True
            )
        }
    )
    def f():
        subprocess.run(["ls", "/my-mount"], check=True)

R2:

Cloudflare R2 is [S3-compatible](https://developers.cloudflare.com/r2/api/s3/api/)
 so its setup looks very similar to S3. But additionally the `bucket_endpoint_url` argument must be passed.

    import subprocess
    
    app = modal.App()
    secret = modal.Secret.from_name(
        "r2-secret",
        required_keys=["AWS_ACCESS_KEY_ID", "AWS_SECRET_ACCESS_KEY"]
    )
    
    @app.function(
        volumes={
            "/my-mount": modal.CloudBucketMount(
                bucket_name="my-r2-bucket",
                bucket_endpoint_url="https://<ACCOUNT ID>.r2.cloudflarestorage.com",
                secret=secret,
                read_only=True
            )
        }
    )
    def f():
        subprocess.run(["ls", "/my-mount"], check=True)

GCS:

Google Cloud Storage (GCS) is [S3-compatible](https://cloud.google.com/storage/docs/interoperability)
. GCS Buckets also require a secret with Google-specific key names (see below) populated with a [HMAC key](https://cloud.google.com/storage/docs/authentication/managing-hmackeys#create)
.

    import subprocess
    
    app = modal.App()
    gcp_hmac_secret = modal.Secret.from_name(
        "gcp-secret",
        required_keys=["GOOGLE_ACCESS_KEY_ID", "GOOGLE_ACCESS_KEY_SECRET"]
    )
    
    @app.function(
        volumes={
            "/my-mount": modal.CloudBucketMount(
                bucket_name="my-gcs-bucket",
                bucket_endpoint_url="https://storage.googleapis.com",
                secret=gcp_hmac_secret,
            )
        }
    )
    def f():
        subprocess.run(["ls", "/my-mount"], check=True)

    __init__(self, bucket_name, bucket_endpoint_url=None, key_prefix=None,
        secret=None, oidc_auth_role_arn=None, read_only=False, requester_pays=False,
        force_path_style=False)

[modal.CloudBucketMount](https://modal.com/docs/sdk/py/latest/modal.CloudBucketMount#modalcloudbucketmount)