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37 .Nd mount a Fuse file system daemon
43 .Op Fl D Ar fuse_daemon
44 .Op Fl O Ar daemon_opts
49 .Op Fl o Ar option ...
51 .Op Ar fuse_daemon ...
53 Basic usage is to start a fuse daemon on the given
56 In practice, the daemon is assigned a
58 file automatically, which can then be indentified via
60 That special file can then be mounted by
63 However, the procedure of spawning a daemon will usually be automated
64 so that it is performed by
66 If the command invoking a given
68 is appended to the list of arguments,
75 will be instructed to attach itself to
77 From that on mounting goes as in the simple case. (See
82 argument will normally be treated as the path of the special file to mount.
90 will look for a suitable free fuse device by itself.
94 is an integer it will be interpreted as the number
95 of the file descriptor of an already open fuse device
96 (used when the Fuse library invokes
101 The options are as follows:
102 .Bl -tag -width indent
103 .It Fl A , Ic --reject-allow_other
107 Intended for use in scripts and the
111 Run in safe mode (i.e. reject invoking a filesystem daemon)
114 .It Fl D, Ic --daemon Ar daemon
117 .It Fl O, Ic --daemon_opts Ar opts
120 to the daemon's command line
121 .It Fl s, Ic --special Ar special
125 .It Fl m, Ic --mountpath Ar node
130 .It Fl V, Ic --version
131 Show version information
133 Mount options are specified via
135 The following options are available (and also their negated versions,
136 by prefixing them with
138 .Bl -tag -width indent
139 .It Cm default_permissions
140 Enable traditional (file mode based) permission checking in kernel
143 .Sx STRICT ACCESS POLICY .
144 Only root can use this option
145 .It Cm max_read Ns = Ns Ar n
146 Limit size of read requests to
149 Refuse shared mounting of the daemon.
150 This is the default behaviour, to allow sharing, expicitly use
152 .It Cm neglect_shares
153 Do not refuse unmounting if there are secondary mounts
154 .It Cm push_symlinks_in
155 Prefix absolute symlinks with the mountpoint
159 Besides the above mount options, there is a set of pseudo-mount options which
160 are supported by the Fuse library.
161 One can list these by passing
164 Most of these options only have affect on the behavior of the daemon (that is,
165 their scope is limited to userspace).
166 However, there are some which do require in-kernel support.
167 Currently the options supported by the kernel are:
168 .Bl -tag -width indent
170 Bypass the buffer cache system
172 By default cached buffers of a given file are flushed at each
174 This option disables this behaviour
177 Usually users do not need to use
179 directly, as the Fuse library enables Fuse daemons to invoke
183 .Dl fuse_daemon device mountpoint
185 has the same effect as
187 .Dl mount_fusefs auto mountpoint fuse_daemon
189 This is the recommended usage when you want basic usage
190 (eg, run the daemon at a low privilege level but mount it as root).
191 .Sh STRICT ACCESS POLICY
192 The strict access policy for Fuse filesystems lets one to use the filesystem
193 only if the filesystem daemon has the same credentials (uid, real uid, gid,
194 real gid) as the user.
196 This is applied for Fuse mounts by default and only root can mount without
197 the strict access policy (i.e. the
201 This is to shield users from the daemon
203 on their I/O activities.
205 Users might opt to willingly relax strict access policy (as far they
206 are concerned) by doing their own secondary mount (See
207 .Sx SHARED MOUNTS ) .
209 A Fuse daemon can be shared (i.e. mounted multiple times).
210 When doing the first (primary) mount, the spawner and the mounter of the daemon
211 must have the same uid, or the mounter should be the superuser.
213 After the primary mount is in place, secondary mounts can be done by anyone
214 unless this feature is disabled by
216 The behaviour of a secondary mount is analogous to that of symbolic
217 links: they redirect all filesystem operations to the primary mount.
219 Doing a secondary mount is like signing an agreement: by this action, the mounter
220 agrees that the Fuse daemon can trace her I/O activities.
221 From then on she is not banned from using the filesystem
222 (either via her own mount or via the primary mount), regardless whether
226 The device name of a secondary mount is the device name of the corresponding
227 primary mount, followed by a '#' character and the index of the secondary
231 System administrators might want to use a custom mount policy (ie., one going
235 The primary tool for such purposes is
239 is capable of invoking an arbitrary program, one must be careful when doing this.
241 is designed in a way such that it makes that easy.
242 For this purpose, there are options which disable certain risky features (i.e.
246 and command line parsing is done in a flexible way: mixing options and
247 non-options is allowed, but processing them stops at the third non-option
248 argument (after the first two has been utilized as device and mountpoint).
249 The rest of the command line specifies the daemon and its arguments.
250 (Alternatively, the daemon, the special and the mount path can be
251 specified using the respective options.) Note that
253 ignores the environment variable
255 and always behaves as described.
257 In general, to be as scripting /
259 friendly as possible, no information has a fixed
260 position in the command line, but once a given piece of information is
261 provided, subsequent arguments/options cannot override it (with the
262 exception of some non-critical ones).
264 .Bl -tag -width ".Ev MOUNT_FUSEFS_SAFE"
265 .It Ev MOUNT_FUSEFS_SAFE
266 This has the same effect as the
269 .It Ev MOUNT_FUSEFS_VERBOSE
270 This has the same effect as the
273 .It Ev MOUNT_FUSEFS_IGNORE_UNKNOWN
276 will ignore uknown mount options.
277 .It Ev MOUNT_FUSEFS_CALL_BY_LIB
278 Adjust behavior to the needs of the FUSE library.
279 Currently it effects help output.
282 Although the following variables do not have any effect on
284 itself, they affect the behaviour of fuse daemons:
285 .Bl -tag -width ".Ev FUSE_DEV_NAME"
288 If not set, the multiplexer path
292 File desciptor of an opened Fuse device to use.
296 If set, the library will not attempt to mount the filesystem, even
297 if a mountpoint argument is supplied.
300 .Bl -tag -width /dev/fuse
302 Fuse device with which the kernel and Fuse daemons can communicate.
304 The multiplexer path.
307 performed on it automatically is passed to a free Fuse device by the kernel
308 (which might be created just for this puprose).
311 Mount the example filesystem in the Fuse distribution (from its directory):
314 .Dl ./fusexmp /mnt/fuse
318 .Dl mount_fusefs auto /mnt/fuse ./fusexmp
320 Doing the same in two steps, using
323 .Dl FUSE_DEV_NAME=/dev/fuse ./fusexmp &&
324 .Dl mount_fusefs /dev/fuse /mnt/fuse
326 A script wrapper for fusexmp which ensures that
328 does not call any external utility and also provides a hacky
329 (non race-free) automatic device selection:
333 .Dl FUSE_DEV_NAME=/dev/fuse fusexmp
334 .Dl mount_fusefs -S /dev/fuse /mnt/fuse \(lq$@\(rq
346 implementation of the Fuse userspace filesystem
347 framework (see http://fuse.sourceforge.net).
349 This user interface is
352 Secondary mounts should be unmounted via their device name.
353 If an attempt is made to unmount them via their filesystem root path,
354 the unmount request will be forwarded to the primary mount path.
355 In general, unmounting by device name is less error-prone than by mount path
356 (although the latter will also work under normal circumstances).
358 If the daemon is specified via the
362 options, it will be invoked via
364 and the daemon's command line will also have an
366 control operator appended, so that we do not have to wait for its termination.
367 You should use a simple command line when invoking the daemon via these options.
370 is treated as a multiplexer if and only if it is literally the same as
374 Other paths which are equivalent with