Some packages rely on FUSE to provide support for additional filesystems not supported by the kernel.

In general, FUSE software are primarily developed for Linux but many of them can also run on macOS. Nixpkgs supports FUSE packages on macOS, but it requires macFUSE to be installed outside of Nix. macFUSE currently isn't packaged in Nixpkgs mainly because it includes a kernel extension, which isn't supported by Nix outside of NixOS.

If a package fails to run on macOS with an error message similar to the following, it's a likely sign that you need to have macFUSE installed.

dyld: Library not loaded: /usr/local/lib/libfuse.2.dylib
Referenced from: /nix/store/w8bi72bssv0bnxhwfw3xr1mvn7myf37x-sshfs-fuse-2.10/bin/sshfs
Reason: image not found
[1]    92299 abort      /nix/store/w8bi72bssv0bnxhwfw3xr1mvn7myf37x-sshfs-fuse-2.10/bin/sshfs

Package maintainers may often encounter the following error when building FUSE packages on macOS:

checking for fuse.h... no
configure: error: No fuse.h found.

This happens on autoconf based projects that use AC_CHECK_HEADERS or AC_CHECK_LIBS to detect libfuse, and will occur even when the fuse package is included in buildInputs. It happens because libfuse headers throw an error on macOS if the FUSE_USE_VERSION macro is undefined. Many projects do define FUSE_USE_VERSION, but only inside C source files. This results in the above error at configure time because the configure script would attempt to compile sample FUSE programs without defining FUSE_USE_VERSION.

There are two possible solutions for this problem in Nixpkgs:

  1. Pass FUSE_USE_VERSION to the configure script by adding CFLAGS=-DFUSE_USE_VERSION=25 in configureFlags. The actual value would have to match the definition used in the upstream source code.
  2. Remove AC_CHECK_HEADERS / AC_CHECK_LIBS for libfuse.

However, a better solution might be to fix the build script upstream to use PKG_CHECK_MODULES instead. This approach wouldn't suffer from the problem that AC_CHECK_HEADERS/AC_CHECK_LIBS has at the price of introducing a dependency on pkg-config.