6. Configuring your Kernel

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 the Linux standard file system (FSSTND).

In this directory you will find at least one README file. This contains an excellent explanation of how to go about configuring and compiling a new kernel. Read this file (it's a good idea to print it out and have a copy handy whilst you are compiling until you have done this enough times to know your way around).

One small note - the current (Linux 1.2.13) make config dialogue does NOT allow you to go backwards - so if you make a mistake in answering one of the questions, exit by typing CTRL C and start again...

You MUST know what cards/devices you have inside your PC if you are going to recompile your kernel!!!

In order to use PPP, you must configure the kernel to include PPP support (PPP requires BOTH pppd AND kernel support for PPP).

The following is an excerpt from the Linux 1.2.13 make config :-

  *
  * Network device support
  *
  Network device support? (CONFIG_NETDEVICES) [n] y
  Dummy net driver support (CONFIG_DUMMY) [n] y
  SLIP (serial line) support (CONFIG_SLIP) [n] n
  PPP (point-to-point) support (CONFIG_PPP) [n] y

If you are concerned about security of your computer and/or LAN whilst connected to the Internet, you may wish to add support for IP firewalls.

Answer the other make config questions according to the hardware in your PC and the features of the Linux operating system you want. Then continue to follow the README to compile and install your new kernel.

NOTE

If you want to set up you Linux machine as a PPP server or internet gateway, you should also include IP forwarding (you will need it!).

Also, the current kernel creates only 4 PPP devices. For multi- port serial cards, you will need to edit the kernel ppp sources to obtain more ports. (See the README.linux file that comes as part of the PPP-2.1.2 distribution)

Once you have installed and rebooted your new kernel, you can start configuring and testing your PPP link.