What is FUSE?¶ FUSE is a userspace filesystem framework. It consists of a kernel module (fuse.ko), a userspace library (libfuse.) and a mount utility (fusermount). One of the most important features of FUSE is allowing secure, non-privileged mounts. This opens up new possibilities for the use of filesystems.

IGN 1 Relay – SBA Fuse, ETC/ECM Fuse, PCM 1 Fuse, INJ 1 Fuse, INJ 2 Fuse PCM 1 15A Powertrain Control Module (PCM). Mass Air Flow (MFS) Sensor. Evaporative Emission (EVAP) Canister Purge Solenoid, Fuel Composition Sensor, Secondary Fuel Pump Relay ETC/ECM 15A Throttle Actuator Control (TAC) INJ 1 15A Fuel Injectors-Odd-Numbered.
Fuse a future such that poll will never again be called once it has completed. This method can be used to turn any Future into a FusedFuture. Normally, once a future has returned Poll::Ready from poll, any further calls could exhibit bad behavior such as blocking forever, panicking, never returning, etc.If it is known that poll may be called too often then this method can be used to ensure.

This is going to be short. I write this tutorial, because a lot of tutorials mention ext4fuse. While it works for some things one experiences quite a few oddities.
Examples of problems I experienced:

everything has only read permissions
it is possible cd into non existing directories
things like recursive copies cause failures
sometimes stuff can't be read correctly

I wrote that everything has only read permissions. This DOES NOT mean that using this approach will give you write access, but that you SEE the right permissions. The effect is that copying over files via ext4fuse will cause you to have files that only be read-only. With this tutorial you will get the right permissions.
In other words: The file system will still be mounted read-only, but the permissions will be correct.
There is three things you need to take care of:

Load the ext2fs kernel module
Mount the partition with -t ext2fs (you need to specify it and it's ext2fs, not ext2!)
Mount it read-only! Trying to mount the partition without -o ro will not work


# Load the kernel module
kldload ext2fs
# mount
mount -t ext2fs -o ro /dev/<device/partition> <mountpoint>
# Exmaples:
mount -t ext2fs -o ro /dev/ad1s1 /mnt/
# Or on a different partition scheme (p vs s):
mount -t ext2fs -o ro /dev/ada0p1 /mnt/

So to repeat the important points. Load the kernel module! Make sure you always write ext2fs, both for the module AND the mount option. Don't forget about the fs part. And make sure to mount it read only.
You can of course add ext2fs to the list of automatically loaded kernel modules, so you don't have to load it over and over again.
In your /etc/rc.conf add:
This will make sure that the kernel module will be loaded on boot. If you already have a kld_list entry then just append ext2fs to it.

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From Wikipedia:

In computing, a file system or filesystem (often abbreviated to fs), controls how data is stored and retrieved. Without a file system, information placed in a storage medium would be one large body of data with no way to tell where one piece of information stops and the next begins. A file system separates the data into pieces and gives each piece a name. Each group of data is called a 'file'.

There are many different kinds of file systems. Each one has different structure and logic, properties of speed, flexibility, security, size and more.

Files and directories themselves are placed on top of the file system, therefore it is common to refer to the file/directory structure itself as 'file system'. On GNU/Linux, the Filesystem Hierarchy Standard defines the naming scheme and hierarchy between files and directories themselves.

File systems usually sit on top of hard disk partitions or LVM volumes. In Debian, ext4 is the default file system for new installations.

GNU/Linux can be installed on any filesystem that supports some special constructs (file permissions, symbolic links and device files).

Many file systems are journaling, meaning they are able to prevent data loss on system crashes or power failures.

Contents

Mounting a filesystem

In GNU/Linux the contents of a filesystem can be made available under a directory, by mounting the filesystem over the directory. Here are some ways to mount a filesystem:

The mount command. For example mount /dev/sdd1 /mn/ would make contents of the first partition of the /dev/sdd disk device, available in the /mnt/ directory.
Editing the fstab file

Filesystems available in Debian Linux kernel

Note0: Debian HURD and Debian kFreeBSD have other file systems.

Note1: the Features list are incomplete at this time.

Note2: This table is uptodate as of 2.6.28 kernel.

Filesystem name	Features?	Documentation(s)	Description	Distributions
File systems often used as linux system partition
ext4	R	(default filesystem in Debian) Fourth Extended Filesystem with extents	>= Squeeze
ext2	RS	kDoc, WPedia	Second Extended Filesystem	All?
ext3	RS	kDoc, WPedia	Second Extended Filesystem with journaling extensions	All?
ext4dev	R	Fourth Extended Filesystem with extents not for production, in development	Etch-n-Half ~ Lenny
jfs	R	The Journaled Filesystem (JFS)	All?
xfs	R	SGI XFS Filesystem	All?
reiserfs	R	ReiserFS journaled filesystem	All?
Other File systems
9p	Plan 9 9p remote filesystem protocol	All?
adfs	Acorn (and Risc OS) Advanced Disc Filing System	All?
affs	I	Amiga filesystem support for Linux	All?
kafs	N	AFS Client File System	All?
autofs4	Auto-mount filesystems. See autofs	All?
autofs	Auto-mount filesystems. See autofs	All?
befs	I	BeOS File System (BeFS) driver	All?
bfs	I	SCO UnixWare BFS filesystem for Linux	All?
btrfs	RS	B-Tree filesystem	>= Jessie
cifs	N I	VFS to access servers complying with the SNIA CIFS Specification e.g. Samba and Windows	All?
coda	Coda Distributed File System VFS interface	All?
configfs	Simple RAM filesystem for user driven kernel subsystem configuration.	All?
cramfs	cram a filesystem onto a small ROM	All?
dlm	Distributed Lock Manager	All?
ecryptfs	eCryptfs	All?
efs	SGI EFS, Extent File System (Irix <0.6)	All?
fat	I	MS & DR DOS FAT filesystem	All?
freevxfs	Veritas Filesystem (VxFS) driver	All?
fuse	Filesystem in Userspace (backend for various filesystems)	All?
gfs2	N	Global File System	All?
hfs	I	Macintosh HFS Fil

Fuse Ext4