MOUNT_PORTAL(8)

NAME
mount_portal - mount the portal daemon

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

DESCRIPTION
The mount_portal command attaches an instance of the portal daemon to the global filesystem namespace. The conventional mount point is /p. 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 configuration 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 call.

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

The following sub-namespaces are currently implemented: tcplisten, tcp and fs. The tcplisten namespace takes a slash separated hostname and port and creates a TCP/IP socket bound to the given hostname-port pair. The hostname may be specified as "ANY" to allow any other host to connect to the socket. A port number of 0 will dynamically allocate a port, this can be discovered by calling getsockname(2) with the returned file descriptor. Privileged ports can only be bound to by the super-user. The tcp namespace takes a hostname and a port (slash separated) and creates an open TCP/IP connection. 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.

CONFIGURATION FILE
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.

    # @(#)portal.conf	5.1 (Berkeley) 7/13/92
    tcplisten/	tcplisten tcplisten/
    tcp/		tcp tcp/
    fs/		file fs/

FILES
/p/*

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

CAVEATS
This filesystem may not be NFS-exported.

HISTORY
The mount_portal utility first appeared in 4.4BSD.