Essential System Administration, 3rd Edition

Adding a New Serial Device

To add a new serial device to the system, you must perform the following steps:

• Physically connect the terminal or modem to the computer.

• Determine the special file in /dev that communicates with the serial line.

• In the case of terminals, make sure a termcap or terminfo entry exists for the kind of terminal you are adding. If none exists, you will have to create one.

• Add or modify an entry in the relevant configuration files (which files to use depends on the desired use: login, dial-up, dial-out, and so on).

• If appropriate, force init to reread the terminal configuration information.

Each of these steps will be considered in turn.

Making the Physical Connection

This section discusses issues related to making the physical connection between a terminal or modem and the computer. It is condensed from the Nutshell Handbook Managing uucp and Usenet, by Grace Todino and Tim O’Reilly (O’Reilly & Associates), with some additions and slight alterations.

The serial cables used to connect computers or terminals to modems are commonly called RS-232 cables; technically, they conform—more or less—to the Electronic Industries Association (EIA) RS-232C or the more recent RS-232D standard. By extension (really by bending, if not breaking, the standard), RS-232 cables have come to be used to connect computers to all kinds of serial devices—terminals, printers, and ports on other computers, as well as modems.

Full RS-232 cables consist of up to 25 wires, each with a specific function ...