Understanding OpenDAL Storage in Dify: A New Year’s Journey

My Story

Happy New Year! 🎉

As 2026 kicks off, I countinue to dive deeper into the AI ecosystem and experimenting with various tools. My focus? Building practical AI workflows with platforms like Dify, n8n, OpenRouter and so on. This post documents one of my first with Dify - figuring out how its file storage actually works.

If you’re like me and got confused about where Dify stores files, why containers keep restarting with cryptic permission errors, or what the heck OPENDAL_FS_ROOT actually does, this guide is for you.

What is This About?

I use self-hosted Dify and run it with docker. I found that the file storage configuration is not well documented, so I decided to write this post to help others understand how it works.

When you’re running Dify with Docker, understanding how file storage works is crucial. Files uploaded to Dify (documents, images, etc.) need to be stored somewhere, and that “somewhere” involves a dance between environment variables, Docker volume mounts, and a library called OpenDAL.

Let me break down what I learned the hard way.

The Key Players

1. OpenDAL - The Unsung Hero

OpenDAL (Apache Open Data Access Layer) is basically a Swiss Army knife for storage. It gives you one consistent API to talk to different storage backends - local filesystem, AWS S3, Azure Blob, you name it. Think of it as a translator that speaks “storage” in many dialects.

2. Environment Variables

Your .env file is where the magic configuration happens. This is where you tell Dify how and where to store files.

3. Docker Volume Mounts

This is the bridge between your Mac (or whatever host you’re on) and the Docker container’s internal filesystem. Get this wrong, and you’ll be scratching your head for hours. Trust me, I know.

How The Pieces Fit Together

Step 1: The Environment Variable Magic

When you set OPENDAL_SCHEME=fs, the system starts looking for variables that match this pattern:

OPENDAL_<SCHEME_NAME>_<CONFIG_NAME>

So for filesystem storage:

• OPENDAL_SCHEME=fs → tells it to use local filesystem
• OPENDAL_FS_ROOT=<path> → tells it where to put files

Simple enough, right? Well, here’s where it gets interesting…

Step 2: What Happens Inside the Container

I dove into the source code (api/extensions/storage/opendal_storage.py) and found this gem:

def _get_opendal_kwargs(*, scheme: str, env_file_path: str = ".env", prefix: str = "OPENDAL_"):
    kwargs = {}
    config_prefix = prefix + scheme.upper() + "_"  # Creates "OPENDAL_FS_"

    # Scans environment variables
    for key, value in os.environ.items():
        if key.startswith(config_prefix):
            kwargs[key[len(config_prefix):].lower()] = value
    # OPENDAL_FS_ROOT becomes kwargs['root']

Then in the OpenDALStorage constructor:

def __init__(self, scheme: str, **kwargs):
    kwargs = kwargs or _get_opendal_kwargs(scheme=scheme)

    if scheme == "fs":
        root = kwargs.get("root", "storage")  # Gets OPENDAL_FS_ROOT value
        Path(root).mkdir(parents=True, exist_ok=True)  # Creates directory inside container

Step 3: The Critical Connection - Volume Mounts

Here’s what tripped me up initially. In docker-compose.yaml, you’ll see:

volumes:
  - ./volumes/app/storage:/app/api/storage
    # ^^^^^^^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^^^
    # Your Mac              Inside container

The “Aha!” Moment:

• Left side (./volumes/app/storage): This is a folder on your actual Mac (relative to where docker-compose.yaml lives)
• Right side (/app/api/storage): This is a folder inside the Docker container (a completely separate filesystem)
• Docker magically keeps these two folders in sync

So when Dify writes a file to /app/api/storage inside the container, it appears in ./volumes/app/storage on your Mac. Mind = blown. 🤯

Real-World Examples

The Default Setup (What Works Out of the Box)

This is what Dify gives you by default, and honestly, it works great:

STORAGE_TYPE=opendal
OPENDAL_SCHEME=fs
OPENDAL_FS_ROOT=/app/api/storage  # Container path - must match volume mount

⚠️ Deprecated Configuration (Do Not Use)

The following configuration is deprecated and should be migrated to OpenDAL:

# DEPRECATED - Old approach
STORAGE_TYPE=local
STORAGE_LOCAL_PATH=storage

Why it’s deprecated:

• STORAGE_TYPE=local is marked as deprecated in the codebase
• STORAGE_LOCAL_PATH is deprecated in favor of OpenDAL’s configuration
• OpenDAL provides a unified interface that supports multiple storage backends

Migration path:

# Before (Deprecated)
STORAGE_TYPE=local
STORAGE_LOCAL_PATH=storage

# After (Current)
STORAGE_TYPE=opendal
OPENDAL_SCHEME=fs
OPENDAL_FS_ROOT=/app/api/storage

The OpenDAL approach offers:

• Unified configuration pattern across all storage types
• Better extensibility (easy to switch to S3, Azure Blob, etc.)
• Improved error handling and retry mechanisms
• Active maintenance and support

volumes:
  - ./volumes/app/storage:/app/api/storage

Result: Files stored in ./volumes/app/storage/ on your Mac

What If I Want Files Somewhere Else?

Maybe you’re like me and want all your AI project files in a specific folder. Here’s how:

# .env (NO CHANGE NEEDED)
STORAGE_TYPE=opendal
OPENDAL_SCHEME=fs
OPENDAL_FS_ROOT=/app/api/storage  # Keep this as container path

# docker-compose.yaml (ONLY change the left side)
volumes:
  - ~/Documents/models/dify_data/files:/app/api/storage
    # ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^^
    # Custom host path                    Same container path

Result: All your Dify files now live in ~/Documents/models/dify_data/files/ on your Mac. Perfect for keeping your AI experiments organized!

Mistakes I Made (So You Don’t Have To)

🤦 Mistake #1: The $HOME Trap

I thought “Hey, I’ll just use $HOME to point to my Documents folder!”

# DON'T DO THIS - I learned the hard way
OPENDAL_FS_ROOT=$HOME/Documents/models/dify_data/files

What happened:

• My containers started crash-looping
• Error logs screamed: PermissionError: [Errno 13] Permission denied: '/Users'
• Spent 2 hours debugging 😅

Why it failed: Inside the Docker container, $HOME is /root, not /Users/yourusername. The container tried to create /Users/yourusername/Documents/... and failed spectacularly.

The fix:

# Always use the container path
OPENDAL_FS_ROOT=/app/api/storage

🤦 Mistake #2: Trying to Be Too Clever

When I wanted a custom storage location, my first instinct was to change OPENDAL_FS_ROOT:

# NOPE - This breaks everything
OPENDAL_FS_ROOT=/my/custom/path

The problem: This path must match the right side of your volume mount. If they don’t match, chaos ensues.

The right way:

• Keep OPENDAL_FS_ROOT=/app/api/storage (container path)
• Only change the left side of the volume mount (your Mac path)

🤦 Mistake #3: Relative Path Confusion

Using relative paths seemed harmless:

# Avoid this
OPENDAL_FS_ROOT=storage  # Where even is this?

The issue: Inside a container, “relative to what?” becomes a real question. Is it relative to /app? /app/api? Who knows!

Better approach:

# Crystal clear - no ambiguity
OPENDAL_FS_ROOT=/app/api/storage

When Things Go Wrong (Debugging Tips)

Symptom: Containers Keep Restarting

This was my first encounter with Dify. Everything would start, then crash, start again, crash again. Fun times.

First, check the logs:

docker-compose logs --tail=50 api

If you see this:

PermissionError: [Errno 13] Permission denied: '/Users'

You might have got the $HOME trap or a path mismatch. Fix OPENDAL_FS_ROOT to use the container path.

My Debugging Checklist

When something’s off, I run through these commands:

1. Check environment variable inside container:

   docker exec docker-api-1 env | grep OPENDAL

2. Check mounted directory:

   docker exec docker-api-1 ls -la /app/api/storage

3. Verify sync with host:

   ls -la ./volumes/app/storage/

Quick Reference (The TL;DR)

Here’s everything in one place:

The Golden Rules:

1. OPENDAL_FS_ROOT always points to a container path (right side of volume mount)
2. Want files elsewhere on your Mac? Change only the left side of the volume mount
3. Never use $HOME or Mac paths in OPENDAL_FS_ROOT
4. When in doubt, use absolute paths

Wrapping Up

This was just one piece of my AI experimentation journey. As I continue exploring Dify, n8n, and the broader AI ecosystem in 2026, I’m sure I’ll encounter more quirks and learning moments. That’s the fun part, right?

If you found this helpful or have your own Dify war stories, I’d love to hear them! This AI revolution is moving fast, and we’re all learning together.

Happy building! 🚀

Useful Links

• Apache OpenDAL Documentation
• OpenDAL Service Configurations
• Dify code: api/extensions/storage/opendal_storage.py
• Agentic Frameworks: A Quick Guide to the 2025 Agent War