NACS > Network > Modems > Connecting with Linux

Using Linux, PPP, and the LifeLine Modem Pool

Summary: These instructions are provided for your convenience. Although it is possible to connect to the modem pool using Linux, the NACS Help Desk does not offer technical support.

First, you should read up on the Lifeline Modem Pool. There's important information about time limits, etc. that you need to know.

The instructions below were developed on a system running Red Hat Linux 5.2. If you are running some other release, you may have to adjust the instructions to make this work.

The new modem pool uses the PAP protocol to authenticate users, so there's no need for the scripts that were used before to "log in" to the old modem pool. PAP is used during PPP initialization, so all you have to do is tell pppd your UCInetID and password and it takes care of the rest.

First, you need to edit /etc/ppp/pap-secrets. You'll need to add a line to the file that looks like this:

# client        server  secret                  IP addresses
jsmith          *       hahahaha        *

Replace "jsmith" with your UCInetID, and "hahahaha" with your UCInetID password.

Next, you need to setup /etc/resolv.conf to have the proper entries so that resolving hostnames to IP addresses works. Put the following lines in the file:

search uci.edu
nameserver 128.200.1.201
nameserver 128.200.192.202

If, for example, you connect to ICS hosts a lot, you can change the first line to

search ics.uci.edu uci.edu

That will take a name like "binky" and try to find it in "ics.uci.edu", then "uci.edu".

Now you need to start pppd. Here's what I use:

 pppd /dev/cua0 57600 user jsmith defaultroute connect \
   'chat "" "at&f1s0=0&n16&u8dt8249999" CONNECT ""'

In a nutshell, the above command starts pppd, which in turn starts chat to talk to the modem on /dev/cua0 (aka COM1). The user jsmith tells pppd what user to look up in /etc/ppp/pap-secrets, and defaultroute tells pppd to setup your default route to be the other end of the connection. See the pppd(8) and the chat(8) man pages for more details on what the above command does. Yes, this doesn't do much error checking. If you want more error checking, you can write a chat script to do it.

You may need to change the setup string in the above example for your modem. The setup string is everything between the "at" and the "dt8249999". You may not need a setup string, so you can remove all the characters between the "at" and the "dt8249999". Most newermodems have a "hardware handshaking" default setup, and that's the one you'll more than likely want to use. If your modem is on something other than /dev/cua0, you'll have to change that as well.

You can put the above line in a script and use that to start pppd. If you make pppd suid root you can start it as a regular user.

If you are having problems getting this to work, you can turn on debugging to see if that tells you what is wrong. To do this, add the debug option to the pppd line before the user option, and setup syslog to log daemon debug messages to the file /var/log/daemon.debug (or some other filename you pick). To do that, you need to edit /etc/syslog.conf and add a line that looks like this:

daemon.debug        /var/log/daemon.debug

The spaces between the two fields are really tabs, so make sure you use tabs or this will not work. Next, you need to:

touch /var/log/daemon.debug
kill -HUP `cat /var/run/syslogd.pid`

This will tell syslogd to reread /etc/syslog.conf and start logging the daemon debugging info to /var/log/daemon.debug. The information in that file should get you started on finding the problem you are having.