How to Implement a File System in Rust (FUSE)

Core
2026-04-17T16:39:40+00:00
You implement a custom file system in Rust by using the `rust-fuse` crate, which provides safe bindings to the Linux FUSE kernel module, allowing you to define file system operations in Rust that the kernel mounts as a virtual directory.

You implement a custom file system in Rust by using the rust-fuse crate, which provides safe bindings to the Linux FUSE kernel module, allowing you to define file system operations in Rust that the kernel mounts as a virtual directory. You define a struct implementing the Filesystem trait, handle operations like getattr and readdir in your logic, and run the mount loop via Fuse::new().

Here is a minimal example creating a virtual file system that returns a single file named hello.txt with the content "Hello from Rust FUSE":

use std::os::unix::io::RawFd;
use std::sync::Arc;
use rust_fuse::Filesystem;
use rust_fuse::mount::Mount;
use rust_fuse::fuse::FileAttr;
use rust_fuse::fuse::FileType;

struct MyFs;

impl Filesystem for MyFs {
    fn getattr(&self, _path: &str, _fh: Option<RawFd>) -> Result<FileAttr, i32> {
        if _path == "/" {
            Ok(FileAttr {
                ino: 1,
                mode: 0o40755,
                nlink: 2,
                uid: 0,
                gid: 0,
                rdev: 0,
                size: 0,
                blksize: 512,
                blocks: 0,
                atime: 0,
                mtime: 0,
                ctime: 0,
                crtime: 0,
                flags: 0,
                generation: 0,
            })
        } else if _path == "/hello.txt" {
            Ok(FileAttr {
                ino: 2,
                mode: 0o100644,
                nlink: 1,
                uid: 0,
                gid: 0,
                rdev: 0,
                size: 17,
                blksize: 512,
                blocks: 8,
                atime: 0,
                mtime: 0,
                ctime: 0,
                crtime: 0,
                flags: 0,
                generation: 0,
            })
        } else {
            Err(libc::ENOENT)
        }
    }

    fn readdir(&self, _path: &str, _fh: Option<RawFd>, _offset: u64, _buffer: &mut [u8]) -> Result<usize, i32> {
        if _path == "/" {
            // Simplified: In a real impl, you'd fill the buffer with directory entries
            // This is a placeholder to show the signature
            Ok(0) 
        } else {
            Err(libc::ENOENT)
        }
    }

    fn read(&self, _path: &str, _fh: RawFd, _buffer: &mut [u8], _offset: u64, _flags: i32) -> Result<usize, i32> {
        if _path == "/hello.txt" {
            let data = b"Hello from Rust FUSE";
            let len = data.len().min(_buffer.len());
            _buffer[..len].copy_from_slice(&data[..len]);
            Ok(len)
        } else {
            Err(libc::ENOENT)
        }
    }
}

fn main() {
    let fs = Arc::new(MyFs);
    let mount = Mount::new("/mnt/my_fuse_fs", fs);
    
    // This blocks until the mount is unmounted or an error occurs
    match mount.mount() {
        Ok(_) => println!("Mounted successfully"),
        Err(e) => eprintln!("Mount failed: {:?}", e),
    }
}

To run this, you need root privileges or fusermount3 installed. Create the mount point and run the binary:

sudo mkdir -p /mnt/my_fuse_fs
cargo run --release

Once running, you can access the file system like any other directory: cat /mnt/my_fuse_fs/hello.txt. Note that rust-fuse is the modern, safe wrapper; older projects might use fuse-rs, but rust-fuse is preferred for new development due to better async support and safety guarantees. Remember that readdir requires careful buffer management to return directory entries correctly, which is omitted here for brevity.