10.4. Patching the Fedora Kernel for MPPE Support

Problem

Oops, you have an older (pre-2.6.15-rc1) kernel on your Fedora, Red Hat, CentOS, or Red Hat-like system. You don't want to upgrade, so you need to build the MPPE kernel module. How do you do this?

Solution

The fine Poptop maintainers use Dynamic Kernel Module Support (DKMS) to generate the MPPE kernel module, which is much easier than the traditional way. First, test for MPPE support:

	# modprobe ppp-compress-18 && echo ok
	FATAL: Module ppp-compress-18 not found.

Then, you need to build a new kernel module. Follow these steps. First, find your kernel version:

	# uname -r
	2.6.11-1.1369.fc6

Then, download the matching kernel-devel package. First, list the available versions:

	# yum search kernel-devel
	[...]
	kernel-devel.i586    2.6.11-1.1369.fc6 core
	Matched from:
	kernel-devel
	[...]

If there is more than one, install the one that matches your kernel:

	# yum install kernel-devel-2.6.11-1.1369_fc4.i586

If there is only one, save yourself some typing:

	# yum install kernel-devel

Now, install the DKMS package, which is a great tool that simplifies building new kernel modules:

	# yum install dkms

Finally, download and install the MPPE module builder RPM (currently dkms-2.0.10-1) from Poptops's Sourceforge download site (http://sourceforge.net/project/showfiles.php?group_id=44827). Reboot, then try loading the MPPE module:

	# modprobe ppp-compress-18 && echo success
	success

Very good! Now you can move on to installing and running your pptpd server.

Discussion

Another way to install the kernel-devel package is to hunt down and download the RPM, then use Yum to install it this way:

	# yum localinstall kernel-devel-2.6.11-1.1369_FC4.i686.rpm

This is an option if you can't find a kernel-devel package with Yum to match your installed kernel. They must match, or your new kernel module might not work.

See Also