Write a filesystem in JavaScript, mount it as a real kernel filesystem.

You can write a driver with the same methods as node:fs/promises (stat, readdir, open, mkdir, rename). Mountx takes your driver and turns it into a real folder on the machine, so ls, cat, AI Agents, VSCode and any other program can use it.

There is no special API to learn: node:fs/promises already is the interface, and the errors it throws already are the error format.

So anything that behaves a bit like a filesystem can get a real path: an in-memory store, a zip file, an S3 bucket, a database, or a plain folder served back out with your own rules on top.

import { mount } from "mountx/auto";
import { createLoopback } from "mountx";
import { createMemoryDriver } from "mountx/drivers/memory";

// A driver is any object with stat(), readdir(), open(), [mkdir()] and [rename()] methods.
// Mountx has built-in memory, fs and unstorage drivers
const driver = createMemoryDriver();

// Work with FS in-process without mounting
const fs = createLoopback(driver);
await fs.mkdir("/notes");
await fs.writeFile("/notes/hello.txt", "hi!");
new TextDecoder().decode(await fs.readFile("/notes/hello.txt")); // "hi"

// Mount the driver to the kernel with whatever this host can use
// FUSE on Linux (no root needed), NFSv3 on macOS
await using mounted = await mount(driver, "/mnt/point", {
  fuse: { attrTimeout: 10 }, // seconds the kernel may cache attributes
});

/**
# /mnt/point is a real folder now, so every program on the machine can use it:
$ cat /mnt/point/notes/hello.txt   =>   hi!
$ echo hey > /mnt/point/notes/other.txt
**/

if (mounted.transport === "fuse") {
  mounted.notifyInvalInode(2n); // storage changed behind mountx's back? drop the cache
}

await mounted.unmount(); // or let `await using` do it at the end of the block

npx nypm i mountx

Or mount a demo filesystem right now, and watch every request the kernel makes:

npx mountx

mountx.vercel.app

• Quick Start — install it and have a folder in about a minute.
• Drivers — the three built-in ones, and the interface for writing your own.
• Mounting — mount(), the mount object, lifecycle and unmount.
• Tuning — caching, concurrency, and the measured numbers.
• Troubleshooting — the things that will bite you, and how to recover.
• Transports — FUSE, 9P and NFS, what each costs, and how to pin one.
• S3 Gateway — serve a driver as an S3-compatible bucket for rclone, the AWS CLI or an SDK, no mount involved.
• WebDAV — serve a driver over RFC 4918 to rclone, curl or davfs2, no mount involved either.
• Reference — every entry point, option and type.

Published under the MIT license 💛.