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GNU/Linux Desktop Survival Guide
by Graham Williams

PPP: Networking Over Modems

For Debian use pppconfig to configure your network connections. This tool will request the appropriate information and knows about chat scripts and PAP connections. It will ask you to name the connection you want to configure, with a default name of provider. It will then generate the appropriate configuration scripts in [ppp]/etc/chatscripts/provider and [ppp]/etc/ppp/peers/provider (the provider in these paths is replaced with the name you supply pppconfig).

The plog command will show you the ppp log which is in [plog]/var/log/ppp.log. To watch the plog file issue the command plog -f as root or else as a user in the group adm.

The pppconfig command allows you to configure your modem connections. Essentially it is a front end to the various scripts in /etc/ppp. My PCMCIA modem is loaded at /dev/ttyS1. Newer versions of ppconfig check the serial ports for modems for you. Usually, /dev/ttyS0 corresponds to COM1 under MS/Windows and /dev/ttyS1 corresponds to COM2.

To allow users other than root to connect through the modem (using the pon and poff pair of commands) add the users to the Unix group "dip":

# adduser kayon dip

Then, next time user kayon logs on he will be in group dip in addition to the other groups he was already in. He will then be able to initiate and terminate a dial up session. However, user kayon does not have access to the log file through the plog command--only root does, presumably for security reasons, since unless you inhibit it, passwords can be displayed there.

Further information on PPP is available from


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