[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: In Need of Advice

RiverWind wrote:
> Hey There,

Note that cross-posting to a large number of lists never works out
very well.  I would hold discussions one at a time.  I have chosen to
reply only to the debian-user list since that is the list to which I
am subscribed.

> I have two computers, a DOS and a Linux box. Now then, I am wanting
> to access my Linux box via my DOS box.

When you say access, what exactly do you mean?  In my mind that
conjures up only one image.  In my mind I would run a serial terminal
emulator on the DOS machine and use it as a serial terminal to the
GNU/Linux machine.  Of course this has advantages and disadvantages.

You old DOS machine probably has a serial port.  Most of the older
machines did.  But your newer GNU/Linux machine might not.  Most of
the newer machines today are no longer providing those included as
standard on the machine.  However it is very easy to use a USB to
serial converter.  I have a couple of such converters on different
machines and they work very well.  Using one of those USB-serial
converters you could easily set it up as a serial console to a machine
that did not originally include a serial port.  However that will only
work once the operating system is loaded.  It will not provide access
to the BIOS nor to the boot time processes.

> I would ultimately like to use my Linux box as my sole ISP.

This statement confuses me.  Your machine is not an ISP.  An ISP is
an internet service provider.  You would connect your machine to your
ISP in order to have access to the larger, and notably hostile,
Internet.  Because this is something you connect to then you should be
able to connect either your DOS machine or your GNU Linux machine to
your ISP and you would only need one of them.

How are you connecting to your ISP now?  By using your DOS machine?
How?  By phone line modem?  By DSL?  By cable modem?  Other?

Broadband is the preferred connection and the majority of broadband
users today connect using either a cable modem or a DSL modem.  Most
of us have happily left phone line modems and the sounds of phone line
connections behind.  I haven't heard a the bong-bong-chime-buzz of a
phone modem connection for a very long time now.

> I do not believe that using my modem in order to dial up my Linux
> machine would work, but I also know that there is such a thing as a
> "NUL" modem cable???

This leads me to believe that you are using a phone line modem to
connect to your ISP.  True?

Yes on the null modem cable.  In RS-232 one wire is the transmit and
another wire is the receive making the cable connections polarized.
This is designed to talk from a computer to a terminal and each had
their own polarity.  A null-modem cable flips those so that two
computers can talk directly without the terminals in the middle.  This
is the DTE and DCE classifications for data terminal equipment and
data computer equipment.

You would use a null modem cable to talk RS-232 serial between two
computers.  Or null modem cable adaptor.  Radio Shack sells such an
adaptor and as I recall it is around five dollars.  With the adaptor
any standard serial cable can be converted into a null modem cable.

Your GNU Linux machine's /etc/inittab file contains a commented out
template line to start a serial terminal "getty" process.  Uncomment
it.  Send init the HUP signal or run 'telinit q' to have init re-read
the /etc/inittab.

That would be very old-school though.  Surely there is a way for you
to use your GNU Linux machine directly.  Then you would not need to
have a serial connection between them.

> How would you good gentles go about putting such a plan as mine
> into action? In other words, how would you go about accessing a
> Linux machine with a DOS system? Is there any special software?
> Would I have to use a USB port? If I am not mistaken, DOS doesn't
> work with USB ports??? Even more desirable would be the ability to
> use the terminal emulator "Commo" as my means of establishing
> contact between the respective systems.

If your GNU Linux machine has a serial port then connect up a null
modem cable between your two computers.  Or use a standard serial
cable with a null-modem adaptor to connect.  On your GNU Linux machine
uncomment the getty entry from /etc/inittab.  The line to uncomment is
the following line:

  T0:23:respawn:/sbin/getty -L ttyS0 9600 vt100

That will start the getty process on the /dev/ttyS0 serial device.  If
you are using a USB-serial converter then the USB device will be
different and that entry will need to be adjusted.  For a USB serial
device the name is something like /dev/ttyUSB0 and so the "ttyS0" part
would need to be changed to be "ttyUSB0" instead.  Here is an example
for a USB device:

  T0:23:respawn:/sbin/getty -L ttyUSBS0 9600 vt100

Notice that "ttyS0" has been changed in that example to "ttyUSB0" for
a USB to serial converter.  The 9600 in the above represents 9600 bits
per second, 8-bits, no parity.

Then with the above getty in place and running you would start Commo
on your DOS machine.  After hitting Enter you should receive a
"login:" prompt from the GNU Linux machine over the serial
connection.  Log into the machine normally.

For this type of connection it probably won't hurt but I would guess
that Commo will insert modem initialization sequences, "AT" commands,
into the startup.  This will confuse the login program.  Okay to leave
while getting things going but it probably means you will need to hit
Enter several times to clear past the extra junk.  You should
configure Commo to not send modem initialization sequences when used
for connecting directly to another computer by serial cable to avoid
that extra junk being sent when there isn't a phone modem in use.

I cannot guess at how difficult this will be for someone without
vision to accomplish.  It is often difficult enough to two get serial
ports to communicate properly when someone is sighted.  However once
it is set up I expect such a configuration would be very reliable.

> I would appreciate any and all advice I can get regarding this
> matter, so that I won't need to pay for an ISP when I already have
> one. Thanks so much in advance.

Just because you can do this serial connection I am not sure it is the
best thing for you to actually do.  (grin)

I would hope that today a GNU Linux machine would be more accessible
than the previous DOS era machines.


Attachment: signature.asc
Description: Digital signature

Reply to: