2.3 Choosing the right device

Some operating systems provide two separate devices for each serial line, one of which is intended especially for gettys. This is NOT a good idea, because it won’t work with mgetty. It is meant for modems used in auto-answer mode.

mgetty picks up the phone by hand, this will only work properly if you use the same device you would use for dialing out. (Some people like to create a symlink /dev/modem for this, but you have to be consistent and use this for all comm programs if you do - otherwise you’ll run into problems with the lock file names).

Here are some examples for different systems:

• SV Unix systems using the FAS serial driver:

  Use ttyF01 etc., (minor number 80+(port number). Do not use ttyFMxxx—mgetty will open the device anyway, but then an open to the “normal” port (without carrier detect) will block.

• SCO Unix systems with the stock serial driver:

  Use the modem-control port (tty2A), not tty2a, because hardware flow control and carrier detection do not work on “lowercase” tty devices.

  The same holds for “smart” serial boards, as specialix, digiboard, …, because they mimic the behaviour of SCO’s sio driver.

• Linux:

  Use /dev/ttyS*, not /dev/cua*. See Linux.

• SunOS, FreeBSD, NetBSD:

  Use /dev/cua*, not /dev/ttyS*. Don’t ask me why it has to be this way, but the other way won’t work. (On SunOS or Solaris, you can find some gory details in the man zs man page).