UbuntuHelp:BadRAM

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https://help.ubuntu.com/community/BadRAM

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This page is currently a scratch pad for my installation of the BadRAM kernel patch. I'll clean this up later. Or you can ;) An alternative to using the BadRAM which I find just as easy is memmap (included by default in at least 8.04), I describe how to use it here: http://gquigs.blogspot.com/2009/01/bad-memory-howto.html More information on the patch can be found here: http://rick.vanrein.org/linux/badram/index.html Information about compiling a custom kernel on Ubuntu can be found here: [KernelCustomBuild] An old thread on the forums is here: http://ubuntuforums.org/showthread.php?t=102254

Overview

Why do this?

You have a computer with a stick of memory that is predictably bad. This means that memory errors only come from the same couple of addresses. With the BadRAM patch, one can tell the kernel not to allow these addresses to be used. I have a 512MB stick of memory that works great, except it has almost a megabyte that returns errors in Memtest, and if I use this memory in my system I often encounter crashes. With the BadRAM patch, I can avoid this problem.

Building the Patch

If the system you are using already has (a) bad stick(s) of memory, you have two options: a) Put good memory in temporarily until you've built the patch b) If memory errors don't show up in lower memory, you can add the "mem=##MB" kernel option to temporarily disable memory above that point. Ex: According to memtest, my stick of memory has errors between 315MB and 325MB. By adding "mem=314MB" I tell the kernel to pretend I only have 314MB. My system will be stable enough to build the patch, at which point I can pass a parameter to ONLY skip the section between 315MB and 325MB (this providing me 502MB of usable memory). Start by following the instructions for building a Custom Kernel linked above. Once you've downloaded the source, apply Rick Vanrein's patch. Then you can build the kernel as normal. Be sure to build the "BadRam" module. After you've built the new kernel, add it to your /boot/grub/menu.list file as an acceptable kernel. Add the parameter listing addresses in memory to avoid. Memtest can provide you with such a list. Boot the system from your new kernel. Success.

My Progress

I relied heavily on az's comments here: http://ubuntuforums.org/showpost.php?p=565328&postcount=7 I followed 'What you'll need' from the [KernelCustomBuild] page. Since I'm not a kernel developer, I next did cd /usr/src sudo apt-get source linux-source Next I unpacked (note that your filename may be different) sudo tar xvjf linux-source-2.6.20.tar.bz2 Download the patch (Check Rick's website for the URL) sudo wget (URL-TO-THE-2.6.20-PATCH) Enter the folder cd linux-source-2.6.20 Copy the existing kernel config from the boot partition sudo cp /boot/config-2.6.20-16-generic .config Apply the kernel patch: sudo patch -p1 < ../BadRAM-2.6.20.1.patch Build the kernel package (Press Y to add support for BADRAM) sudo make-kpkg --initrd --append-to-version=-badram --stem=linux kernel_image kernel_headers Install the new kernel package and kernel headers package sudo dpkg -i linux-image-(whatever)-badram.deb sudo dpkg -i linux-headers-(whatever)-badram.deb On reboot, everything seemed to work fine except XOrg. I couldn't get X to start even with the nv driver. I've yet to figure out how to build the restricted-drivers package against the custom kernel headers installed in the step above. Still to add: running memtest and determining the bad memory addresses; editing /etc/grub/menu.lst to block those bad memory addresses; building restricted-drivers package to facilitate the use of vmware-player, nvidia drivers, etc from aptitude.