Provided by: fuse_2.9.4-1ubuntu3.1_amd64 bug


       fuse - format and options for the fuse file systems


       FUSE  (Filesystem  in  Userspace) is a simple interface for userspace programs to export a
       virtual filesystem to the Linux kernel. FUSE also aims to provide a secure method for  non
       privileged users to create and mount their own filesystem implementations.


       Some options regarding mount policy can be set in the file /etc/fuse.conf. Currently these
       options are:

       mount_max = NNN
              Set the maximum number of FUSE mounts allowed to non-root  users.  The  default  is

              Allow  non-root  users  to specify the allow_other or allow_root mount options (see


       Most of the generic mount options described in mount are supported (ro, rw, suid,  nosuid,
       dev,  nodev,  exec, noexec, atime, noatime, sync, async, dirsync). Filesystems are mounted
       with nodev,nosuid by default, which can only be overridden by a privileged user.

   General mount options:
       These are FUSE specific mount options that can be specified for all filesystems:

              By default FUSE doesn't check file access permissions, the filesystem  is  free  to
              implement  it's  access  policy or leave it to the underlying file access mechanism
              (e.g. in case of network filesystems). This  option  enables  permission  checking,
              restricting  access  based on file mode.  This is option is usually useful together
              with the allow_other mount option.

              This option overrides the security measure restricting  file  access  to  the  user
              mounting the filesystem.  So all users (including root) can access the files.  This
              option is by default only allowed to root, but this restriction can be removed with
              a configuration option described in the previous section.

              This  option  is  similar  to  allow_other  but  file access is limited to the user
              mounting the filesystem  and  root.   This  option  and  allow_other  are  mutually

              This  option  disables  flushing  the  cache of the file contents on every open(2).
              This should only be enabled on filesystems, where the file data  is  never  changed
              externally  (not through the mounted FUSE filesystem).  Thus it is not suitable for
              network filesystems and other intermediate filesystems.

              NOTE: if this option is not specified (and neither direct_io) data is still  cached
              after  the  open(2),  so  a  read(2)  system  call  will not always initiate a read

              This option enables automatic flushing of the data cache on open(2). The cache will
              only be flushed if the modification time or the size of the file has changed.

              Issue  large read requests.  This can improve performance for some filesystems, but
              can also degrade performance. This option is only useful on 2.4.X  kernels,  as  on
              2.6 kernels requests size is automatically determined for optimum performance.

              This  option  disables the use of page cache (file content cache) in the kernel for
              this filesystem. This has several affects:

       1.     Each read(2) or write(2) system call will  initiate  one  or  more  read  or  write
              operations, data will not be cached in the kernel.

       2.     The  return  value  of  the  read() and write() system calls will correspond to the
              return values of the read and write operations. This is useful for example  if  the
              file size is not known in advance (before reading it).

              With  this  option  the  maximum size of read operations can be set. The default is
              infinite. Note that the size of read requests is limited anyway to 32 pages  (which
              is 128kbyte on i386).

              Set  the  maximum  number of bytes to read-ahead.  The default is determined by the
              kernel. On linux-2.6.22 or earlier it's 131072 (128kbytes)

              Set the maximum number of bytes  in  a  single  write  operation.  The  default  is
              128kbytes.   Note,  that due to various limitations, the size of write requests can
              be much smaller (4kbytes). This limitation will be removed in the future.

              Perform reads asynchronously. This is the default

              Perform all reads (even read-ahead) synchronously.

              The default behavior is that if an open file is deleted, the file is renamed  to  a
              hidden  file (.fuse_hiddenXXX), and only removed when the file is finally released.
              This relieves the filesystem implementation of having to deal  with  this  problem.
              This  option  disables the hiding behavior, and files are removed immediately in an
              unlink operation (or in a rename operation which overwrites an existing file).

              It is recommended that you not use the hard_remove option. When hard_remove is set,
              the  following  libc  functions fail on unlinked files (returning errno of ENOENT):
              read(2),  write(2),  fsync(2),  close(2),   f*xattr(2),   ftruncate(2),   fstat(2),
              fchmod(2), fchown(2)

       debug  Turns on debug information printing by the library.

              Sets  the  filesystem  source  (first field in /etc/mtab). The default is the mount
              program name.

              Sets the filesystem type (third field in  /etc/mtab).  The  default  is  the  mount
              program  name. If the kernel suppports it, /etc/mtab and /proc/mounts will show the
              filesystem type as fuse.TYPE

              If the kernel doesn't support subtypes, the source filed will be TYPE#NAME,  or  if
              fsname option is not specified, just TYPE.

              Honor  the st_ino field in kernel functions getattr() and fill_dir(). This value is
              used to fill in the st_ino field in the stat(2), lstat(2), fstat(2)  functions  and
              the  d_ino  field  in  the  readdir(2)  function.  The  filesystem does not have to
              guarantee uniqueness, however some applications rely on this value being unique for
              the whole filesystem.

              If use_ino option is not given, still try to fill in the d_ino field in readdir(2).
              If the name was previously looked up, and is still in the cache, the  inode  number
              found  there  will  be  used. Otherwise it will be set to -1.  If use_ino option is
              given, this option is ignored.

              Allows mounts over a non-empty file or directory.  By  default  these   mounts  are
              rejected to prevent accidental covering up of data, which could for example prevent
              automatic backup.

              Override the permission bits in  st_mode  set  by  the  filesystem.  The  resulting
              permission  bits  are  the  ones  missing from the given umask value.  The value is
              given in octal representation.

       uid=N  Override the st_uid field set by the filesystem (N is numeric).

       gid=N  Override the st_gid field set by the filesystem (N is numeric).

       blkdev Mount a filesystem backed by a block device.  This  is  a  privileged  option.  The
              device must be specified with the fsname=NAME option.

              The  timeout  in  seconds for which name lookups will be cached. The default is 1.0
              second. For all the timeout options, it is possible to give fractions of  a  second
              as well (e.g. entry_timeout=2.8)

              The timeout in seconds for which a negative lookup will be cached. This means, that
              if file did not exist (lookup retuned ENOENT), the lookup will only be redone after
              the  timeout,  and the file/directory will be assumed to not exist until then.  The
              default is 0.0 second, meaning that caching negative lookups are disabled.

              The timeout in seconds for which file/directory attributes are cached.  The default
              is 1.0 second.

              The  timeout  in  seconds  for  which file attributes are cached for the purpose of
              checking if auto_cache should flush the file data on   open.  The  default  is  the
              value of attr_timeout

       intr   Allow  requests to be interrupted.  Turning on this option may result in unexpected
              behavior, if the filesystem does not support request interruption.

              Specify  which  signal  number  to  send  to  the  filesystem  when  a  request  is
              interrupted.  The default is hardcoded to USR1.

              Add  modules  to  the  filesystem  stack.  Modules are pushed in the order they are
              specified, with the original filesystem being on the bottom of the stack.


       Modules are filesystem stacking support to high level API. Filesystem modules can be built
       into libfuse or loaded from shared object

       Perform file name character set conversion.  Options are:

              Character set to convert from (see iconv -l for a list of possible values). Default
              is UTF-8.

              Character set to convert to.  Default is determined by the current locale.

       Prepend a given directory to each path. Options are:

              Directory to prepend to all paths.  This option is mandatory.

              Transform absolute symlinks into relative

              Do not transform absolute symlinks into relative.  This is the default.


       The fusermount program is installed set-user-gid to fuse. This is done to allow users from
       fuse  group  to  mount  their  own filesystem implementations.  There must however be some
       limitations, in order to prevent Bad  User  from  doing  nasty  things.   Currently  those
       limitations are:

       1.     The user can only mount on a mountpoint, for which it has write permission

       2.     The  mountpoint  is not a sticky directory which isn't owned by the user (like /tmp
              usually is)

       3.     No other user (including root) can access the contents of the mounted filesystem.


       FUSE filesystems are unmounted using the fusermount(1) command (fusermount -u mountpoint).


       The main author of FUSE is Miklos Szeredi <>.

       This man page was written by Bastien  Roucaries  <>  for
       the Debian GNU/Linux distribution (but it may be used by others) from README file.


       fusermount(1) mount(8)