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FUSE (Filesystem in Userspace) is a simple interface for userspace
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programs to export a virtual filesystem to the linux kernel. FUSE
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also aims to provide a secure method for non privileged users to
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create and mount their own filesystem implementations.
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You can download the source code releases from
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http://sourceforge.net/projects/fuse
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or alternatively you can use CVS to get the very latest development
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version by setting the cvsroot to
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:pserver:anonymous@cvs.sourceforge.net:/cvsroot/fuse
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and checking out the 'fuse' module.
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You may also need to add '/usr/local/lib' to '/etc/ld.so.conf' and/or
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For more details see the file 'INSTALL'
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FUSE is made up of three main parts:
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- A kernel filesystem module
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- A mount/unmount program
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Here's how to create your very own virtual filesystem in five easy
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steps (after installing FUSE):
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1) Edit the file example/fusexmp.c to do whatever you want...
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2) Build the fusexmp program
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3) run 'example/fusexmp /mnt/fuse -d'
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If it doesn't work out, please ask! Also see the file 'include/fuse.h' for
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detailed documentation of the library interface.
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If you run 'make install', the fusermount program is installed
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set-user-id to root. This is done to allow normal users to mount
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their own filesystem implementations.
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There must however be some limitations, in order to prevent Bad User from
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doing nasty things. Currently those limitations are:
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- The user can only mount on a mountpoint, for which it has write
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- The mountpoint is not a sticky directory which isn't owned by the
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user (like /tmp usually is)
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- No other user (including root) can access the contents of the mounted
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Some options regarding mount policy can be set in the file
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Currently these options are:
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Set the maximum number of FUSE mounts allowed to non-root users.
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Allow non-root users to specify the 'allow_other' or 'allow_root'
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These are FUSE specific mount options that can be specified for all
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By default FUSE doesn't check file access permissions, the
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filesystem is free to implement it's access policy or leave it to
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the underlying file access mechanism (e.g. in case of network
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filesystems). This option enables permission checking, restricting
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access based on file mode. This is option is usually useful
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together with the 'allow_other' mount option.
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This option overrides the security measure restricting file access
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to the user mounting the filesystem. This option is by default only
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allowed to root, but this restriction can be removed with a
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configuration option described in the previous section.
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This option is similar to 'allow_other' but file access is limited
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to the user mounting the filesystem and root.
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This option disables flushing the cache of the file contents on
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every open(). This should only be enabled on filesystems, where the
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file data is never changed externally (not through the mounted FUSE
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filesystem). Thus it is not suitable for network filesystems and
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other "intermediate" filesystems.
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NOTE: if this option is not specified (and neither 'direct_io') data
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is still cached after the open(), so a read() system call will not
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always initiate a read operation.
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Issue large read requests. This can improve performance for some
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filesystems, but can also degrade performance. This option is only
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useful on 2.4.X kernels, as on 2.6 kernels requests size is
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automatically determined for optimum performance.
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This option disables the use of page cache (file content cache) in
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the kernel for this filesystem. This has several affects:
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- Each read() or write() system call will initiate one or more
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read or write operations, data will not be cached in the
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- The return value of the read() and write() system calls will
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correspond to the return values of the read and write
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operations. This is useful for example if the file size is not
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known in advance (before reading it).
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With this option the maximum size of read operations can be set.
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The default is infinite. Note that the size of read requests is
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limited anyway to 32 pages (which is 128kbyte on i386).
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The default behavior is that if an open file is deleted, the file is
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renamed to a hidden file (.fuse_hiddenXXX), and only removed when
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the file is finally released. This relieves the filesystem
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implementation of having to deal with this problem. This option
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disables the hiding behavior, and files are removed immediately in
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an unlink operation (or in a rename operation which overwrites an
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Turns on debug information printing by the library.
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Sets the filesystem name. The default is the program name.
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