May 23, 2009

Fedora 11, Kernel-PAE, and What it Means for Your x86-32 System

Article Source Fedora Community
May 23, 2009, 7:09 pm
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There is one small change in Fedora 11 that I guess will confuse Fedora and RPM Fusion users with x86-32 (aka i386/ix86) systems quite a lot, but afaics did not get enough attention yet:

âÃúAppropriateâÃù is not really explained âÃî maybe because itâÃôs a bit hard to sum up without going into the boring details. But basically it boils down to: The kernel with PAE support will be installed by Fedora 11 for x86-32 on the majority of x86-compatible systems that have been manufactured in the past three or four years(¬Ï). So likely on your system as well if you are running a x86-32 distro on a modern system.

The important part: the package containing the kernel with PAE support is not called âÃúkernelâÃù âÃî itâÃôs called âÃúkernel-PAEâÃù instead. And thatâÃôs not the only package where âÃú-PAEâÃù is used as suffix. That has major certain consequences on systems where Fedora 11 installs kernel-PAE:

  • when you build kernel modules with akmods, dkms, or manually, then you from now on need to install kernel-devel-PAE instead of kernel-devel
  • similar for kernel-modules: instead of âÃúyum install kmod-nvidiaâÃù your now need to type âÃúyum install kmod-nvidia-PAEâÃù. Yum otherwise will try to install the matching kernel without PAE support for you, which (in short without the boring details) is something you most of the time donâÃôt want(¬â¤).

In other words: the change in Fedora 11 makes lots of howtos, FAQs, articles on the net and in computer magazines confusing, wrong, misleading or harmful (depending on view and specific howto/FAQ/article), because most of those docs donâÃôt consider the above fact (yet).

And thatâÃôs not FedoraâÃôs fault âÃî PAE kernels are around for a long time in Fedora already. But they were used only on a minority of systems. Most (not all!) of those that have written todayâÃôs howtos, FAQs or articles were likely either not aware of it or chose to ignored it to keep things simple.

ThatâÃôs backfiring now. So go and spread the news on mailing lists, forums and other places where it might be of interest. Feel free to copy-n-paste this whole text or simply point to this blog entry. Thanks in advance!

(¬Ï) E.g. since processors with NX bit became mainstream; NX stands for NoeXecute and is also called Enhanced Virus Protection by AMD and xD-Bit by Intel

(¬â¤) not sure, but maybe the yum-plugin âÃúyum-fedorakmodâÃù could have made yum to the right thing and install the proper kmod for the PAE kernel. I never tried and it doesnâÃôt matter much as the plugin is not available in the Fedora or RPM Fusion repositories for F11. If someone wants take care of yum-fedorakmod and wants to get it into RPM Fusion then please drop me a line.

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