For creating devices in the device directory see
Creating Devices In the /dev directory
Devices in Linux have major and minor numbers. Each serial port may have 2 possible names in the /dev directory: ttyS and cua. Their drivers behave slightly differently. The cua device is deprecated and will not be used in the future. See the Modem-HOWTO section: "The cua Device".
Dos/Windows use the COM name while the setserial program uses
tty00, tty01, etc. Don't confuse these with dev/tty0, dev/tty1, etc.
which are used for the console (your PC monitor) but are not serial
ports. The table below is for the "standard" case (but yours could be
different).
IO
dos major minor major minor address
COM1 /dev/ttyS0 4, 64; /dev/cua0 5, 64 3F8
COM2 /dev/ttyS1 4, 65; /dev/cua1 5, 65 2F8
COM3 /dev/ttyS2 4, 66; /dev/cua2 5, 66 3E8
COM4 /dev/ttyS3 4, 67; /dev/cua3 5, 67 2E8
linux% ls -l /dev/cua*
linux% ls -l /dev/ttyS*
On some installations, two extra devices will be created,
/dev/modem for your modem and /dev/mouse for your
mouse. Both of these are symbolic links to the appropriate
device in /dev which you specified during the
installation (unless you have a bus mouse, then /dev/mouse
will point to the bus mouse device).
There has been some discussion on the merits of /dev/mouse
and /dev/modem. The use of these links is discouraged. In
particular, if you are planning on using your modem for dialin you may
run into problems because the lock files may not work correctly if you
use /dev/modem. However, if you change or remove this
link, some applications might need reconfiguration.
If you don't have a device, you will have to create it with the
mknod command or with the MAKEDEV shell script. Example, suppose
you needed to create ttyS0:
linux# mknod -m 666 /dev/cua0 c 5 64 (cua devices are now obsolete)
linux# mknod -m 666 /dev/ttyS0 c 4 64
MAKEDEV script, which lives in /dev.
See the man page for it. This simplifies the making of devices. For
example, if you needed to make the devices for ttyS0 you
would type:
linux# cd /dev
linux# ./MAKEDEV ttyS0