Recall that a device file is an HP-UX file that "points" to
a system device. The system administrator
often uses the name of the device file when configuring software
to access that device. When devices are connected to an HP-UX MUX
(multiplexer), they are assigned to tty device file names.
When devices are connected to a DTC server, they are assigned to
random pty device file names
. To the user logging on at his terminal from either a MUX or a
DTC, the terminal functions the same way. The user does not see
how the device file is assigned to the connection, and whether the
MUX driver or the terminal server driver is used.
The HP-UX System Administrator creates a device file for each
MUX port, using the HP-UX insf or mknod
command.
Each device file maps to a specific physical MUX port, and device
files are named by convention, so that each identifies a unique
MUX port.
For example, /dev/tty2p3 means port 3 on
MUX card 2.
A device connected to a DTC
or other terminal server communicates with the system via Telnet.
Therefore, it is considered to be a logical device, and it is serviced
by a pseudoterminal device driver (pty).
It is referenced using its pty
device file name.
Usually, this pty is assigned to the Telnet connection randomly
from a pool of free ptys
in the /dev directory or subdirectories at
connection setup time. In many cases, the randomness of pty assignments
for Telnet
users is acceptable, because the physical location of the Telnet
user is unimportant. In fact, users of system-to-system Telnet have
always been subject to this situation. However, when a specific
DTC device must always be associated with the same pty, then the
randomness of pty assignments must be removed through a utility
such as DDFA.
Starting with HP-UX 10.0, pty device files for incoming connections
should be assigned to the directory /dev/telnet
so that they can be more easily tracked and be correctly displayed
by commands such as ps -ef.
