Provided by: fuse_2.8.6-2ubuntu2_i386 bug

NAME

       fuse - format and options for the fuse file systems

DESCRIPTION

       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.

CONFIGURATION

       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 1000.

       user_allow_other
              Allow non-root users to specify the  allow_other  or  allow_root
              mount options (see below).

OPTIONS

       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:

       default_permissions
              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.

       allow_other
              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.

       allow_root
              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 exclusive.

       kernel_cache
              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 operation.

       auto_cache
              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.

       large_read
              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.

       direct_io
              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).

       max_read=N
              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).

       max_readahead=N
              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)

       max_write=N
              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.

       async_read
              Perform reads asynchronously. This is the default

       sync_read
              Perform all reads (even read-ahead) synchronously.

       hard_remove
              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.

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

       subtype=TYPE
              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.

       use_ino
              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.

       readdir_ino
              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.

       nonempty
              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.

       umask=M
              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.

       entry_timeout=T
              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)

       negative_timeout=T
              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.

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

       ac_attr_timeout=T
              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.

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

       modules=M1[:M2...]
              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.

FUSE MODULES (STACKING)

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

   iconv
       Perform file name character set conversion.  Options are:

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

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

   subdir
       Prepend a given directory to each path. Options are:

       subdir=DIR
              Directory to prepend to all paths.  This option is mandatory.

       rellinks
              Transform absolute symlinks into relative

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

SECURITY

       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.

NOTE

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

AUTHORS

       The main author of FUSE is Miklos Szeredi <mszeredi@inf.bme.hu>.

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

SEE ALSO

       fusermount(1) mount(8)

                                                                       fuse(8)