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Use an old serial VT100 terminal with OS X – Mac OS X Hints January 21, 2015

Posted by sandyclaus in Academic Technology.
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Old VT-100 serial (RS232) terms can often be found for free in the computer trashes of various institutions like universities. I use mine as a terminal in a room away from my main computer location, but it could also be useful as a cheap second monitor dedicated to command-line work, to display logs or man pages, or as a jukebox interface in parties to avoid exposing your computer to spilled beer or other liquids (just run the lynx text web browser and some form of web remote control for iTunes). It costs almost nothing and is cool, maybe even useful!

Hardware: apart from the terminal itself, you need the appropriate type of serial cables (depends on hardware you have), a serial port, and a null modem. The old beige G3 is the only OSX supported computer that have the appropriate built-in serial ports. If you’re not the lucky owner of such a machine, you can use a USB – RS232 interface (I do have a beige G3, so I do not have tested this with USB, but it should work as well).

Basically, you simply connect the serial connector of the old terminal to the null modem (whose function is to swap transmit and receive lines), then the null modem to the serial connector of your computer.

Configuration: from the command line, backup the original ttys file by typing sudo cp /etc/ttys /etc/ttys.orig. Edit /etc/ttys with your favorite text editor as administrator to enable login from the serial line — change the line:

tty.serial “/usr/libexec/getty serial.9600” vt100 off secure

to the line:

tty.printer “/usr/libexec/getty serial.9600” vt100 on secure

Notes: I use tty.printer, which is the printer port on my beige G3. Obviously, use tty.modem if you connect your old terminal to the modem port. I don’t know the appropriate device for a USB-RS232 interface. If someone try this, please post the info here. Also, your old terminal should be set at 9600 baud. If you use 19200 baud instead, use serial.19200.

Final step: next time you reboot with your old terminal properly connected and configured for VT100 mode and 9600 baud, you should get a login prompt on it. Enter your login and password, and you’re now able to run any command you like!

via Use an old serial VT100 terminal with OS X – Mac OS X Hints.

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