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NetBSD 6.1.5 - man page for mount_portal (netbsd section 8)

MOUNT_PORTAL(8) 		   BSD System Manager's Manual			  MOUNT_PORTAL(8)

     mount_portal -- mount the portal daemon

     mount_portal [-o options] /etc/portal.conf mount_point

     The mount_portal command attaches an instance of the portal daemon to the global filesystem
     namespace.  The conventional mount point is /p.  The directory specified by mount_point is
     converted to an absolute path before use.	This command is normally executed by mount(8) at
     boot time.

     The options are as follows:

     -o      Options are specified with a -o flag followed by a comma separated string of
	     options.  See the mount(8) man page for possible options and their meanings.

     The portal daemon provides an open service.  Objects opened under the portal mount point are
     dynamically created by the portal daemon according to rules specified in the named configu-
     ration file.  Using this mechanism allows descriptors such as sockets to be made available
     in the filesystem namespace.

     The portal daemon works by being passed the full pathname of the object being opened.  The
     daemon creates an appropriate descriptor according to the rules in the configuration file,
     and then passes the descriptor back to the calling process as the result of the open system

     By convention, the portal daemon divides the namespace into sub-namespaces, each of which
     handles objects of a particular type.

     Currently, four sub-namespaces are implemented: tcp, fs, rfilter and wfilter.  The tcp
     namespace takes a hostname and a port (slash separated) and creates an open TCP/IP connec-
     tion.  The fs namespace opens the named file, starting back at the root directory.  This can
     be used to provide a controlled escape path from a chrooted environment.

     The rfilter and wfilter namespaces open a pipe to a process, typically a data-filter such as
     compression or decompression programs.  The rfilter namespace opens a read-only pipe, while
     the wfilter namespace opens a write-only pipe.  See the EXAMPLES section below for more

     The configuration file contains a list of rules.  Each rule takes one line and consists of
     two or more whitespace separated fields.  A hash (``#'') character causes the remainder of a
     line to be ignored.  Blank lines are ignored.

     The first field is a pathname prefix to match against the requested pathname.  If a match is
     found, the second field tells the daemon what type of object to create.  Subsequent fields
     are passed to the creation function.

     The rfilter and wfilter namespaces have additional meanings for the remaining fields.  The
     third field specifies a prefix that is to be stripped off of the passed name before passing
     it on to the pipe program.  If the prefix does not match, no stripping is performed.  The
     fourth argument specifies the program to use for the pipe.  Any remaining fields are passed
     to the pipe program.  If the string ``%s'' exists within these remaining fields, it will be
     replaced by the path after stripping is performed.  If there is no field after the program
     name, ``%s'' will be assumed, to maintain similarity with the tcp and fs namespaces.


     A tutorial and several examples are provided in /usr/share/examples/mount_portal.	The fol-
     lowing is an example configuration file.

     # @(#)portal.conf	     5.1 (Berkeley) 7/13/92
     tcp/	     tcp tcp/
     fs/	     file fs/
     echo/	     rfilter echo/   echo %s
     echo_nostrip/   rfilter nostrip echo %s
     echo_noslash    rfilter echo_noslash    echo %s
     gzcat/	     rfilter gzcat/ gzcat %s
     gzip/	     wfilter gzip/   gzip > %s
     gzip9/	     wfilter gzip9/  gzip -9 > %s
     ftp/	     rfilter ftp/    ftp -Vo - %s
     ftp://	     rfilter nostrip ftp -Vo - %s
     http://	     rfilter nostrip ftp -Vo - %s
     bzcat/	     rfilter bzcat/  bzcat %s
     nroff/	     rfilter nroff/  nroff -man %s

     As is true with many other filesystems, a weird sense of humor is handy.

     Notice that after the keynames, like nroff/ and bzcat/, we typically use another slash.  In
     reality, the mount_portal process changes directory to /, which makes the subsequent slash
     unnecessary.  However, the extra slash provides a visual hint that we are not operating on
     an ordinary file.	An alternative would be to change the configuration file to something

     nroff%  rfilter nroff%  nroff -man

     One might then use

     less /p/nroff%/usr/share/man/man8/mount_portal.8

     mount(2), unmount(2), fstab(5), mount(8)

     The mount_portal utility first appeared in 4.4BSD.  The rfilter and wfilter capabilities
     first appeared in NetBSD 1.5.  The portal kernel driver was removed and mount_portal was
     converted to use puffs(3) in NetBSD 6.0.

     This filesystem may not be NFS-exported.

BSD					 December 5, 2009				      BSD

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