man(1) Manual page archive


     MNT(3)                                                     MNT(3)

     NAME
          mnt - attach to 9P servers

     SYNOPSIS
          #M

     DESCRIPTION
          The mount driver is used by the mount system call (but not
          bind; see bind(2)) to connect the name space of a process to
          the service provided by a 9P server over a communications
          channel.  After the mount, system calls involving files in
          that portion of the name space will be converted by the
          mount driver into the appropriate 9P messages to the server.

          The mount system call issues an auth(5) message to the
          server to validate the user and an attach(5) message to
          identify the user of the connection.  Each distinct user of
          a connection must mount it separately; the mount driver mul-
          tiplexes the access of the various users and their processes
          to the service.

          File-oriented system calls are converted by the kernel into
          messages in the 9P protocol.  Within the kernel, 9P is
          implemented by procedure calls to the various kernel device
          drivers.  The mount driver translates these procedure calls
          into remote procedure calls to be transmitted as messages
          over the communication channel to the server.  Each message
          is implemented by a write of the corresponding protocol mes-
          sage to the server channel followed by a read on the server
          channel to get the reply.  Errors in the reply message are
          turned into system call error returns.

          A read(2) or write system call on a file implemented by the
          mount driver may be translated into more than one message,
          since there is a maximum data size for a 9P message.  The
          system call will return when the specified number of bytes
          have been transferred or a short reply is returned.

          The string `#M' is an illegal file name, so this device can
          only be accessed directly by the kernel.

     BUGS
          It is not possible to mount a service through the mount
          driver across a network.  As a result the window command
          will not work from the CPU server since it cannot mount the
          srv entry for 8½.

     SEE ALSO
          bind(2)