This is a binding to FUSE for the OCaml programming language, enabling you to write multithreaded filesystems in the OCaml language. It has been designed with simplicity as a goal, as you can see by looking at example/fusexmp.ml. Efficiency has also been a separate goal. The Bigarray library is used for read and writes, allowing the library to do zero-copy in OCaml land.
Published: 24 May 2023
This repository is cloned from the last CVS snapshot of OCamlFuse, with:
Fix for a race condition in multi-threaded mode (see #4).
See all the merged PR
This is a binding to
fuse for the OCaml programming language, enabling you to write multithreaded filesystems with the OCaml language. It has been designed with simplicity as a goal, as you can see by looking at
example/fusexmp.ml. Efficiency has also been a separate goal. The
Bigarray library is used for read and writes, allowing the library to do zero-copy in OCaml land.
fuse (version 2.7 or greater)
You also need
OCaml >= 4.02.3 and
camlidl >= 1.05.
The recommended way to install this library is with opam.
opam install ocamlfuse
If you don't want to install
opam, you need to manually install this prerequisites:
Should be in the major linux distributions, but you can find it at
You need to install
libfuse-devin debian and ubuntu.
OCaml >= 4.02.3
Should be in the major linux distributions, but is also available at
CamlIDL >= 1.05
present at least in ubuntu, also available at
dune >= 3.7
unpack the tarball, then
make make install
This will install ocamlfuse in your ocaml library directory. To uninstall it you can run
make example cd _build/default/example mkdir tmp ./fusexmp.exe tmp cd tmp #you'll find a copy of your "/" directory here
NOTE: if you access the "clone" of the mountpoint of the filesystem, the fs will hang (kill it and then use fusermount -u to umount it). This is a known bug/limitation.
BEFORE YOU WRITE YOUR OWN FILESYSTEM
KNOWN PROBLEMS (if you can help, please do)
The stateful interface for readdir is not implemented
There is a stub in
st_blocks- if one implements statfs with a block size different than 512 "du" will not work on the filesystem.
many ocaml exceptions are reported as 127
we should add non-blocking
*xattrimplementations for ocaml in
translation between ocaml unix errors and C unix error is dependent on the order of constructor names in ocaml. There should be a way to get error names from caml and create a translation table.
Unix_utillibrary uses unsafe coercions between unix file handles (which are defined as ints) and ints. Even if this works, in the future it might stop working.
writeoperations have not been tested in case of errors. Error code conversion might be incorrect but I don't have test cases (maybe the easy way is to modify fusexmp to return various errors).
Unix errors which are unknown to ocaml should be reported as EUNKNOWNERR
Test statfs (never used until now)
Some errors are missing in the unix module (e.g. ENOTSUP,ENOATTR, see man lsxattr). We could solve all these problems with errors using a custom error type instead of
unix_errorbut this would create troubles.
deadlock (and consequent necessity to kill -KILL the program) if accessing the mountpoint mirrored inside the mountpoint in fusexmp. I remember it was easy to understand why, but right now I have no idea.
HELPING THE PROJECT
The best help you can give to the project is to test everything, including, but not limited to:
large file operations (files >= 4gb)
multithreaded operations: the filesystem should always be responsive, no matter if reading a certain file blocks
robustness: the filesystem should NEVER exit from its mainloop if not explicitly requested from the user.
Please report if you do serious tests! We need to know which programs did you use, if you found any bug, and how to reproduce the tests.
Also, we need packaging, I don't have the necessary time and don't know ocamlfindlib or GODI. Please if you have the time and the necessary knowledge help with packaging. Autoconf support would be highly appreciated, too.
A mailing list has been set up on sourceforge, you are strongly encouraged to post feedback there and in general to subscribe if you use ocamlfuse.
The sourceforge page for ocamlfuse is
Bye and have fun
vincenzo_ml at yahoo dot it ciancia at di dot unipi dot it applejack at users dot sourceforge dot net