NetBSD now offers full support for running file systems in userspace. The
core component inside the kernel that exposes a file system interface
towards the userland programs is "puffs", and communicates with vnodes,
the kernel's own idea of files. The "libpuffs" library is the interface
between userland file systems and the kernel component. To facilitate
running the huge amount of file systems already available for the FUSE
interface, but not dictate the capabilities of puffs by it, it was decided
that FUSE support should be provided as a compatibility layer on top of
the native puffs interface. This compatibility is offered by re-fuse, a
BSD-licensed re-implementation of FUSE. It is designed to be source code
compatible with FUSE, and more information can be found in the refuse(3)
manpage.

While puffs is stable for users, the library programming interface and the
binary interfaces are still likely to change, and therefore puffs and the
dependant librefuse and not built by default. For people tracking
-current, the build of all relevant puffs components (librefuse, psshfs,
etc.) by make build can be enabled by adding "MKPUFFS=yes" to
/etc/mk.conf. Using puffs also requires the kernel option "file-system
PUFFS", or alternatively loading the puffs.o kernel module, which is
included in a puffs-enabled build.

FUSE compatibility was added within pkgsrc, and besides the required
infrastructure work a number of FUSE packages were added to pkgsrc in the
new "filesystem" category. Example packages that are currently available
include:

   o fuse: Filesystem in Userspace (compat headers, pkg-config files,
     etc.), needed for pkgsrc on Linux
   o fuse-archivemount: FUSE gateway to libarchive
   o fuse-cddfs: FUSE filesystem that uses libparanoia for audio CDs
   o fuse-cryptofs: FUSE encrypted filesystem
   o fuse-curlftpfs: FUSE filesystem for acessing FTP hosts
   o fuse-httpfs: FUSE HTTP filesystem
   o fuse-lzofs: Filesystem which allows you to transparently use
     compressed files
   o fuse-ntfs-3g: NTFS driver with read and write support
   o fuse-unionfs: FUSE-based union filesystem

puffs was originally developed during the Google Summer of Code 2005
"userfs" project by Antti Kantee. It was further polished using funding
from the Ulla Tuominen Foundation and committed into the NetBSD source
tree in October 2006. The work was presented at AsiaBSDCon 2007 in a paper
entitled "puffs - Pass-to-Userspace Framework File System". The "refuse"
library was written by Alistair Crooks and committed to NetBSD in February
2007. All components will be available in NetBSD releases starting with
NetBSD 5. Work for using FUSE-enabled packages via pkgsrc was done by Juan
Romero Pardines following import of the "refuse" library.  Hubert Feyrer
was the editor of this announcement and prepared the puffs webpage.

For more information, see NetBSD's webpage on file systems in userspace at
http://www.NetBSD.org/Documentation/misc/puffs.html