In order to use PPP, your Linux kernel must be compiled to include PPP support. Obtain the Linux source code for your kernel if you do not already have this - it belongs in /usr/src/linux on Linux's standard file system.
Check out this directory - many Linux distributions install the source tree (the files and subdirectories) as part of their installation process.
At bootup, your Linux kernel prints out a great deal of information. Amongst this is information about PPP support and if the kernel includes it. To view this information, look at your syslog file or use
dmesg | less |
PPP Dynamic channel allocation code copyright 1995 Caldera, Inc. PPP line discipline registered. |
(this is for the Linux 2.x.x kernel series).
Linux kernel sources can be obtained by ftp from sunsite.unc.edu or its mirror sites.