FUSE (Filesystem in Userspace) is an interface for userspace programs to export a filesystem to the Linux kernel. The FUSE project consists of two components: the fuse kernel module (maintained in the regular kernel repositories) and the libfuse userspace library (maintained in this repository). libfuse provides the reference implementation for communicating with the FUSE kernel module.
A FUSE file system is typically implemented as a standalone application that links with libfuse. libfuse provides functions to mount the file system, unmount it, read requests from the kernel, and send responses back. libfuse offers two APIs: a "high-level", synchronous API, and a "low-level" asynchronous API. In both cases, incoming requests from the kernel are passed to the main program using callbacks. When using the high-level API, the callbacks may work with file names and paths instead of inodes, and processing of a request finishes when the callback function returns. When using the low-level API, the callbacks must work with inodes and responses must be sent explicitly using a separate set of API functions.
You can download libfuse from https://github.com/libfuse/libfuse/releases. After extracting the tarball, build and install with
./configure
make -j8
make install
You may also need to add /usr/local/lib to /etc/ld.so.conf and/or
run ldconfig. If you're building from the git repository (instead of
using a release tarball), you also need to run ./makeconf.sh to
create the configure script.
You'll also need a fuse kernel module (Linux kernels 2.6.14 or later contain FUSE support).
For more details see the file INSTALL
If you run make install, the fusermount program is installed
set-user-id to root. This is done to allow normal users to mount
their own filesystem implementations.
There must however be some limitations, in order to prevent Bad User from doing nasty things. Currently those limitations are:
-
The user can only mount on a mountpoint, for which it has write permission
-
The mountpoint is not a sticky directory which isn't owned by the user (like /tmp usually is)
-
No other user (including root) can access the contents of the mounted filesystem (though this can be relaxed)
FUSE comes with several example file systems in the examples
directory. For example, the fusexmp example mirrors the contents of
the root directory under the mountpoint. Start from there and adapt
the code!
The documentation of the API functions and necessary callbacks is
mostly contained in the files include/fuse.h (for the high-level
API) and include/fuse_lowlevel.h (for the low-level API).
If you need help, please ask on the [email protected] mailing list (subscribe at https://lists.sourceforge.net/lists/listinfo/fuse-devel).
Please report any bugs on the GitHub issue tracker at https://github.com/libfuse/libfuse/issues.
libfuse is currently maintained by Nikolaus Rath.
The CUSE feature was added by Tejun Heo.
FUSE (both libfuse and the kernel module) was written by Miklos Szeredi.