getty is a program that handles the login process when you log
onto a Linux box. You will need to use getty if you want others
to be able to dial in to your Linux machine with a modem. You do not
need to use getty if you only want to dial out with your modem.
There are three getty versions that are commonly used with Linux:
getty_ps, mgetty and agetty. The syntax for these
programs differs, so be sure to check that you are using the correct
syntax for whatever getty you use.
Most distributions come with the getty_ps package installed.
(Debian uses agetty.) It contains two programs: getty is used
for console and terminal devices, and uugetty for modems. Greg
Hankins (former author of Serial-HOWTO) used uugetty so his
writings about it are included here. See
Uugetty. The other gettys are covered by the documentation
that comes with them.
mgetty is a version of getty mainly for use with modems. It
may be used for hard-wired terminals but the documentation is about
99% related to modems. In addition to allowing dialup logins,
mgetty also provides FAX support and auto PPP detection. The
mgetty documentation (supplied in texinfo format) is good, and
does not need supplementing. Please refer to it for installation
instructions. You can find the latest information on mgetty at
http://www.leo.org/~doering/mgetty/.
agetty is the third variation of getty. It's a simple,
completely functional implementation of getty which is best
suited for virtual consoles or terminals rather than modems. But it
works fine with modems under favorable conditions.
mingetty is a small getty that will work only for consoles
(monitors). While the previous 3 variations of getty will work for
both real terminals and dial-in modems, mingetty will not do this.
setserial is a program which allows you to tell the device driver
software the I/O address of the serial port, which IRQ it uses, etc.
With appropriate options, it can also probe for serial ports (but you
must know the I/O address). Setserial does not set either IRQ's nor
I/O addresses in the serial port hardware itself. You must tell
setserial the identical values that have been set in the hardware:
either by jumpers or by plug-and-play. Do not just invent some values
that you think would be nice to use. However if you don't know the
IRQ you may command setserial to attempt to determine it.
You can see a list of possible arguments to use by typing
setserial with no arguments. Note that setserial calls an I/O
address a "port". If the argument to setserial is for example just
/dev/ttyS1, then you'll see some info about how that device driver
is configured for that port. But this doesn't tell you if the
hardware actually has these values set in it. If fact, you can run
setserial and assign a purely fictitious I/O address, any IRQ, and
whatever uart type you would like to have. Then the next time you
type "setserial ..." it will display these bogus values without
complaint. Note that assignments made by setserial are lost when the
PC is powered down so it is usually run each time that Linux is
booted.
In order to try to find out if you have a certain piece of serial
hardware you must first know its I/O address (or the device driver
must have an I/O address for it, likely previously set by setserial).
To try to detect the physical hardware use the -v (verbose) and
autoconfig arguments to setserial. If the resulting message
shows a uart type such as 16550, then you're OK. If instead it shows
"unknown" for the uart type, then there may be no serial port at
that I/O address. Some cheap serial ports don't identify themselves
correctly so if you see "unknown" you still might have something
there. See the file which runs "setserial". Besides auto-probing for
uart type, setserial can auto-probe for IRQ's.
When your Linux system boots, only ttyS{0-3} are configured,
using the default IRQs of 4 and 3. In 1998 it was (temporarily ?)
changed to only ttyS{0-1}. By default, both ttyS0 and ttyS2
share IRQ 4, while ttyS1 and ttyS3 share IRQ 3. But if you only have
two serial ports ttyS0 and ttyS1 you're OK since sharing conflicts
don't exist for non-existent devices.
But if you do have more than 2 serial ports, then such sharing may be dangerous if the two devices with the same IRQ are being used at the same time. That is, unless you have special software designed for IRQ sharing. If you add an internal modem and retain ttyS0 and ttyS1, then you should attempt to find an unused IRQ and set it both on your modem card (or serial port) and then use setserial to assign it to your device driver. You may need to use isapnp to set it. To help you determine which spare IRQ's you may use, type "man setserial" and search for say: "IRQ 11".
Note that setserial will only work if the kernel module "serial" has
been loaded. See the man page for setserial as well as the supplied
file which runs it at start-up (which may contain a number of
commented-out examples). In 1998, due to motherboards with defective
serial chips Linux doesn't do autoconfiguration on ttyS{2-3} as
it formerly did.
If you use setserial you could test it on the command line first,
and then when you have it working, put it into
/etc/rc.d/rc.serial or /etc/rc.d/rc.local or
/etc/rc.boot/0setserial so that it is run at startup. Or you
could just edit the above file and cross your fingers. Make sure that
you are using a valid path for setserial, and a valid device
name.
isapnp is a program to configure Plug-and-Play (PnP) devices
on the ISA bus including internal modems. It comes in a package
called "isapnptools" and includes another program, "pnpdump" which
finds all your ISA PnP devices and shows their current configuration
in a format which may be added to the PnP configuration file:
/etc/isapnp.conf. The isapnp command may be put into a startup file
so that it run each time you start the computer and thus will
configure ISA PnP devices. It is able to do this even if your BIOS
doesn't support PnP. See Plug-and-Play-HOWTO.