Man

Command Section
MOUNT_FUSEFS(8)         FreeBSD System Manager's Manual        MOUNT_FUSEFS(8)

NAME
     mount_fusefs - mount a Fuse file system daemon

SYNOPSIS
     mount_fusefs [-A] [-S] [-v] [-D fuse_daemon] [-O daemon_opts]
                  [-s special] [-m node] [-h] [-V] [-o option ...]
                  special node [fuse_daemon ...]

DESCRIPTION
     Basic usage is to start a fuse daemon on the given special file.  In
     practice, the daemon is assigned a special file automatically, which can
     then be indentified via fstat(1).  That special file can then be mounted
     by mount_fusefs.

     However, the procedure of spawning a daemon will usually be automated so
     that it is performed by mount_fusefs.  If the command invoking a given
     fuse_daemon is appended to the list of arguments, mount_fusefs will call
     the fuse_daemon via that command.  In that way the fuse_daemon will be
     instructed to attach itself to special.  From that on mounting goes as in
     the simple case. (See DAEMON MOUNTS.)

     The special argument will normally be treated as the path of the special
     file to mount.

     However, if auto is passed as special, then mount_fusefs will look for a
     suitable free fuse device by itself.

     Finally, if special is an integer it will be interpreted as the number of
     the file descriptor of an already open fuse device (used when the Fuse
     library invokes mount_fusefs.  (See DAEMON MOUNTS).

     The options are as follows:

     -A, --reject-allow_other
             Prohibit the allow_other mount flag.  Intended for use in scripts
             and the sudoers(5) file.

     -S, --safe
             Run in safe mode (i.e. reject invoking a filesystem daemon)

     -v      Be verbose

     -D, --daemon daemon
             Call the specified daemon

     -O, --daemon_opts opts
             Add opts to the daemon's command line

     -s, --special special
             Use special as special

     -m, --mountpath node
             Mount on node

     -h, --help
             Show help

     -V, --version
             Show version information

     -o      Mount options are specified via -o.  The following options are
             available (and also their negated versions, by prefixing them
             with ``no''):

             default_permissions
                     Enable traditional (file mode based) permission checking
                     in kernel

             allow_other
                     Do not apply STRICT ACCESS POLICY.  Only root can use
                     this option

             max_read=n
                     Limit size of read requests to n

             private
                     Refuse shared mounting of the daemon.  This is the
                     default behaviour, to allow sharing, expicitly use -o
                     noprivate

             neglect_shares
                     Do not refuse unmounting if there are secondary mounts

             push_symlinks_in
                     Prefix absolute symlinks with the mountpoint

     Besides the above mount options, there is a set of pseudo-mount options
     which are supported by the Fuse library.  One can list these by passing
     -h to a Fuse daemon.  Most of these options only have affect on the
     behavior of the daemon (that is, their scope is limited to userspace).
     However, there are some which do require in-kernel support.  Currently
     the options supported by the kernel are:

     direct_io
             Bypass the buffer cache system

     kernel_cache
             By default cached buffers of a given file are flushed at each
             open(2).  This option disables this behaviour

DAEMON MOUNTS
     Usually users do not need to use mount_fusefs directly, as the Fuse
     library enables Fuse daemons to invoke mount_fusefs.  That is,

           fuse_daemon device mountpoint

     has the same effect as

           mount_fusefs auto mountpoint fuse_daemon

     This is the recommended usage when you want basic usage (eg, run the
     daemon at a low privilege level but mount it as root).

STRICT ACCESS POLICY
     The strict access policy for Fuse filesystems lets one to use the
     filesystem only if the filesystem daemon has the same credentials (uid,
     real uid, gid, real gid) as the user.

     This is applied for Fuse mounts by default and only root can mount
     without the strict access policy (i.e. the allow_other mount option).

     This is to shield users from the daemon ``spying'' on their I/O
     activities.

     Users might opt to willingly relax strict access policy (as far they are
     concerned) by doing their own secondary mount (See SHARED MOUNTS).

SHARED MOUNTS
     A Fuse daemon can be shared (i.e. mounted multiple times).  When doing
     the first (primary) mount, the spawner and the mounter of the daemon must
     have the same uid, or the mounter should be the superuser.

     After the primary mount is in place, secondary mounts can be done by
     anyone unless this feature is disabled by private.  The behaviour of a
     secondary mount is analogous to that of symbolic links: they redirect all
     filesystem operations to the primary mount.

     Doing a secondary mount is like signing an agreement: by this action, the
     mounter agrees that the Fuse daemon can trace her I/O activities.  From
     then on she is not banned from using the filesystem (either via her own
     mount or via the primary mount), regardless whether allow_other is used
     or not.

     The device name of a secondary mount is the device name of the
     corresponding primary mount, followed by a '#' character and the index of
     the secondary mount; e.g.  /dev/fuse0#3.

SECURITY
     System administrators might want to use a custom mount policy (ie., one
     going beyond the vfs.usermount sysctl).  The primary tool for such
     purposes is sudo(8).  However, given that mount_fusefs is capable of
     invoking an arbitrary program, one must be careful when doing this.
     mount_fusefs is designed in a way such that it makes that easy.  For this
     purpose, there are options which disable certain risky features (i.e.  -S
     and -A), and command line parsing is done in a flexible way: mixing
     options and non-options is allowed, but processing them stops at the
     third non-option argument (after the first two has been utilized as
     device and mountpoint).  The rest of the command line specifies the
     daemon and its arguments.  (Alternatively, the daemon, the special and
     the mount path can be specified using the respective options.) Note that
     mount_fusefs ignores the environment variable POSIXLY_CORRECT and always
     behaves as described.

     In general, to be as scripting / sudoers(5) friendly as possible, no
     information has a fixed position in the command line, but once a given
     piece of information is provided, subsequent arguments/options cannot
     override it (with the exception of some non-critical ones).

ENVIRONMENT
     MOUNT_FUSEFS_SAFE      This has the same effect as the -S option.

     MOUNT_FUSEFS_VERBOSE   This has the same effect as the -v option.

     MOUNT_FUSEFS_IGNORE_UNKNOWN
                            If set, mount_fusefs will ignore uknown mount
                            options.

     MOUNT_FUSEFS_CALL_BY_LIB
                            Adjust behavior to the needs of the FUSE library.
                            Currently it effects help output.

     Although the following variables do not have any effect on mount_fusefs
     itself, they affect the behaviour of fuse daemons:

     FUSE_DEV_NAME      Device to attach.  If not set, the multiplexer path
                        /dev/fuse is used.

     FUSE_DEV_FD        File desciptor of an opened Fuse device to use.
                        Overrides FUSE_DEV_NAME.

     FUSE_NO_MOUNT      If set, the library will not attempt to mount the
                        filesystem, even if a mountpoint argument is supplied.

FILES
     /dev/fuse  Fuse device with which the kernel and Fuse daemons can
                communicate.

     /dev/fuse  The multiplexer path.  An open(2) performed on it
                automatically is passed to a free Fuse device by the kernel
                (which might be created just for this puprose).

EXAMPLES
     Mount the example filesystem in the Fuse distribution (from its
     directory): either

           ./fusexmp /mnt/fuse

     or

           mount_fusefs auto /mnt/fuse ./fusexmp

     Doing the same in two steps, using /dev/fuse0:

           FUSE_DEV_NAME=/dev/fuse ./fusexmp &&
           mount_fusefs /dev/fuse /mnt/fuse

     A script wrapper for fusexmp which ensures that mount_fusefs does not
     call any external utility and also provides a hacky (non race-free)
     automatic device selection:

           #!/bin/sh -e

           FUSE_DEV_NAME=/dev/fuse fusexmp
           mount_fusefs -S /dev/fuse /mnt/fuse "[email protected]"

SEE ALSO
     fstat(1), mount(8), sudo(8), umount(8)

HISTORY
     mount_fusefs appeared in FreeBSD 10.0 as the part of the FreeBSD
     implementation of the Fuse userspace filesystem framework (see
     http://fuse.sourceforge.net).

CAVEATS
     This user interface is FreeBSD specific.  Secondary mounts should be
     unmounted via their device name.  If an attempt is made to unmount them
     via their filesystem root path, the unmount request will be forwarded to
     the primary mount path.  In general, unmounting by device name is less
     error-prone than by mount path (although the latter will also work under
     normal circumstances).

     If the daemon is specified via the -D and -O options, it will be invoked
     via system(3), and the daemon's command line will also have an ``&''
     control operator appended, so that we do not have to wait for its
     termination.  You should use a simple command line when invoking the
     daemon via these options.

BUGS
     special is treated as a multiplexer if and only if it is literally the
     same as auto or /dev/fuse.  Other paths which are equivalent with
     /dev/fuse (eg., /../dev/fuse) are not.

FreeBSD 11.1-RELEASE-p4         October 3, 2016        FreeBSD 11.1-RELEASE-p4
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