Red Hat Linux supports common serial devices, such as:
Serial devices attach to a computer through an external interface, either a 9-pin or 25-pin RS-232 connector, known as a serial port.
Alternatively, an internal device might be assigned a logical serial port, through the computer's BIOS.
External and internal devices, although of the same type and similar functionality, might not have the same characteristics.
For example, external and internal modems both connect two computers over a phone line. External modems are completely separate devices that operate
without the support of the computer's CPU. Internal modems usually cannot function as standalone devices and require the operating system to
assist them. Linux supports all external modems, but only a handful of internal modems.
The getty daemon
and its variants support serial communications under Linux. Commonly used protocols over serial lines include PPP and
SLIP. The getty daemon
allows users to log in to a Linux station using a serial device,
which is allocated a terminal (tty). getty assigns each user a different tty session to communicate between themselves and the machine.
A daemon is a program that waits for a request from another program. The daemon then performs the desired
action, such as creating an http session, or opening and maintaining a communications socket. Some common daemons include httpd, telnetd, and
The next lesson explains how to administer serial ports.