---
title: fusion
description: Reference for the fusion config scope, which provides advanced configuration for the use of the Fusion file system.
---

# `fusion`

The `fusion` scope provides advanced configuration for the use of the [Fusion file system][fusion-page].

##### `fusion.cacheSize`

<AddedInVersion version="24.04" />

The maximum size of the local cache used by the Fusion client.

##### `fusion.containerConfigUrl`

The URL of the container layer that provides the Fusion client.
Supports `http(s)://...` and `file:/...` (absolute, no authority) schemes. The latter is intended for local development against a custom manifest.
For example, `file:/path/to/manifest.json`.

##### `fusion.enabled`

Enable the Fusion file system (default: `false`).

##### `fusion.exportStorageCredentials`

Export access credentials required by the underlying object storage as environment variables (e.g., `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`, and `AWS_SESSION_TOKEN` for AWS S3) to task execution environments (default: `false`).

:::note
This configuration does not mount or provide access to credential files. For example, AWS credentials like `~/.aws/credentials`, `~/.aws/config`, and SSO cache files are not mounted. AWS SSO users must export credentials to environment variables:

```bash
eval "$(aws configure export-credentials --format env)"
```
:::

:::warning
This option leaks credentials is the task launcher script. It should only be used for testing and development purposes.
:::

##### `fusion.logLevel`

The log level of the Fusion client.

##### `fusion.logOutput`

The output location of the Fusion log.

##### `fusion.privileged`

<AddedInVersion version="23.10" />

Enable privileged containers for Fusion (default: `true`).
Non-privileged use is supported only on Kubernetes with the [k8s-fuse-plugin](https://github.com/nextflow-io/k8s-fuse-plugin) or a similar FUSE device plugin.

##### `fusion.snapshots`

<AddedInVersion version="25.04" />

*Currently only supported for AWS Batch*

Enable Fusion snapshotting (preview, default: `false`). This feature allows Fusion to automatically restore a job when it is interrupted by a spot reclamation.

##### `fusion.tags`

*Currently only supported for S3.*

The pattern that determines how tags are applied to files created via the Fusion client (default: `[.command.*|.exitcode|.fusion.*](nextflow.io/metadata=true),[*](nextflow.io/temporary=true)`). Set to `false` to disable tags.

[fusion-page]: ../../fusion
