What is needed to implement a custom file system?

[mikelsr]

Let me start by apologizing in advance if this is not the place to ask this, and asking you to point me to the correct place.

I am creating a custom [FileSystem](https://github.com/wasmerio/wasmer/blob/037aa4b861a4211a06eb98edc20076a9c0b400e3/lib/virtual-fs/src/lib.rs#L87) by implementing the [FileSystem](https://github.com/wetware/ww/blob/7f78a2ff0e97573e98bfa6b999a283cd62deb5f8/lib/fs/src/lib.rs#L33), [FileOpener](https://github.com/wetware/ww/blob/7f78a2ff0e97573e98bfa6b999a283cd62deb5f8/lib/fs/src/lib.rs#L92) and [VirtualFile](https://github.com/wetware/ww/blob/7f78a2ff0e97573e98bfa6b999a283cd62deb5f8/lib/fs/src/lib.rs#L198) traits. The custom file system is configured in this line.

The file system is just a wrapper that allows WASM guest programs to read (and only read) from IPFS. Here is the guest program I am using for testing.

When examining the calls made in Wasmer, I find I am getting to this error branch in path_open, but I am unsure of why.

Is there anything I am not implementing, configuring properly...? I'm attaching a segment of the logs at the end of this post.

Thank you in advance!

2024-11-14T14:54:56.515147Z DEBUG wasmer_wasix::fs: Initializing WASI filesystem
2024-11-14T14:54:56.517502Z TRACE wasmer_wasix::state::func_env: initializing with layout WasiMemoryLayout { stack_upper: 1048576, stack_lower: 0, guard_size: 0, stack_size: 1048576 }
2024-11-14T14:54:56.517941Z TRACE fd_prestat_get: wasmer_wasix::syscalls::wasi::fd_prestat_get: return=Errno::success fd=3
2024-11-14T14:54:56.518209Z TRACE fd_prestat_dir_name: wasmer_wasix::syscalls::wasi::fd_prestat_dir_name: return=Errno::success fd=3 path="/"
2024-11-14T14:54:56.518270Z TRACE fd_prestat_get: wasmer_wasix::syscalls::wasi::fd_prestat_get: return=Errno::badf fd=4
2024-11-14T14:54:56.518486Z TRACE path_open:new_open_options: fs: return=OpenOptionsConfig { read: true, write: false, create_new: false, create: false, append: false, truncate: false } dirfd=3 follow_symlinks=true path="ipfs/QmeeD4LBwMxMkboCNvsoJ2aDwJhtsjFyoS1B9iMXiDcEqH"
2024-11-14T14:54:56.518563Z TRACE path_open: wasmer_wasix::syscalls::wasi::path_open: return=Ok(Errno::notcapable) dirfd=3 follow_symlinks=true path="ipfs/QmeeD4LBwMxMkboCNvsoJ2aDwJhtsjFyoS1B9iMXiDcEqH"
Error reading from file: Capabilities insufficient (os error 76)

[Arshia001]

Hey @mikelsr!

Lots of code in WASIX assumes the file system is always created through the use of RootFileSystemBuilder. Can you try mounting your custom file system in a sub-directory? You can look at the WASIX code in the Wasmer CLI as a sample.