pmt(7)                          TCP/IP R4.11                          pmt(7)


NAME
       pmt - pseudo magnetic tape device interface

DESCRIPTION
       This character special device provides indirect access to files on
       magnetic tape.  The tape device and its host are remote entities
       across a network.  Use the open(2) system call to open any of the
       /dev/pmt/* special files and perform I/O on them as if they were
       local tape devices.

       The file /etc/pmttapetab provides the mapping between local (pseudo)
       and remote (real) tape devices.  The remote tape devices listed in
       this file must conform to the rmt(7) interface for pmt to act as a
       character special device.

       To create the pmt special files, the device driver entry pmt() must
       be listed in the system(4) file before configuring the system.
       Configuration variables exist in the master(4) file dgux and in the
       system(4) file to control the number of pmt special files created.

       The pmtd(1M) server must be running on the local machine for any of
       the pmt special files to be successfully opened.

FILES
       /dev/pmt/*        Tape device names for character special access.
       /etc/pmttapetab   Table with information about remote tape devices.

SEE ALSO
       config(1M), pmtd(1M), ioctl(2), open(2), master(4), pmttapetab(4),
       system(4), rmt(7)

CAVEATS
       An ioctl(2) call with the command MTIOCGET does not return the status
       of the remote (real) tape device.  It returns a meaningless status
       for the local (pseudo) tape device.

       If the network is down, processes using a file descriptor for an
       already opened pmt unit may hang while accessing the unit.  Processes
       trying to open(2) a pmt unit can be successfully interrupted.

BUGS
       Any ioctl(2) calls with command set to MTIOCTOP will inherit the bug
       list from pmtd(1M).


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