Kernel Panic: CPU Too Old

Ever see that message? I got it in February when I put Ubuntu 7.10 Server Edition on my roommate's laptop. Jdong pointed me at a bug explaining the problem. I don't believe I ever mentioned it here, but I was just on the phone with a friend, and he said he had this weird problem where it said the CPU was wrong instead of booting. "CPU too old, you mean?" "Yeah, that's it" "Server Edition?" "Yep"

The reason it's doing this is that the -server kernel expects PAE, which lets PCI devices be mapped above the 4GiB line so if you have 4GiB, you can actually use all 4 instead of having your PCI devices be mem-mapped right over where your memory should go and right out of the range of what 32bit can handle.

To fix it, get out a live cd and chroot into the hard drive. sudo chroot /dev/sda1, assuming first drive, first partition (change sda1 to whatever corresponds to your partition if this is not the case). Once in there, run sudo apt-get install linux-image-386, or, if you have a dual-core processor (so you can get SMP), sudo apt-get install linux-image-generic. Then, remove the -server kernel by entering sudo apt-get remove linux-image-$(uname -r) in your terminal. After a reboot, it should, well, be able to boot.

Off-Topic: Survey for Students in the US, Please Take

My roommate works for GenderPAC and helped to create the 2008 GENIUS Survey. She needs students from all around the country to fill out the survey, and she asked me to post here to try to find more people to take it.

The Gender Public Advocacy Coalition is pleased to announce the release of its 2008 Gender Equality National Index for Universities and Schools (GENIUS) Survey. GenderPAC works to ensure that classrooms and communities are safe for everyone to learn, grow and succeed, whether or not they fit expectations for masculinity or femininity. The GENIUS Index tracks and evaluates colleges, universities, and K–12 schools' progress to ensure their campuses are GenderSAFE™—safe, supportive and equitable for all students. Complete the GENUIS survey and send a strong public statement that bullying or discriminating based on the race, sex or gender of a student, faculty, or staff member is not tolerated at your institution. Fill out the survey at: www.gpac.org/GENIUS2008survey and help support campuses working to build safe and welcoming environments for every student.

Having issues with an i945 & Compiz on Hardy?

On IRC a couple days ago, someone popped up with an Intel i945 unable to get Compiz to start. He'd get output like this:

/usr/bin/compiz.real (core) - Fatal: No GLXFBConfig for default depth, this isn't going to work.
/usr/bin/compiz.real (core) - Error: Failed to manage screen: 0
/usr/bin/compiz.real (core) - Fatal: No manageable screens found on display :0.0

That's pretty confusing and un-helpful. To top it off, I have an i945GM which has always worked perfectly. It seemed a lot of people agreed with "but...it's Intel. Intel always just works with Compiz...that's not right!" JDong said something had to be seriously wrong if an i945 wasn't working with Compiz. He was kind of right. I'd say anything in the kernel falls into the category of "serious," but what was actually wrong in the kernel was, thankfully, not huge. He found Bug #204762, which applies to this case. He linked to an upstream change in the Linux kernel which shows the exact problem. The bug has been marked for 8.04.1, due in July.

There are two cards called i945. Go figure. The version in my laptop is the GMA. The version in his computer is the GME. Guess what else? The kernel in Hardy knows what mine is. It has no idea what his is, beyond that it uses the intel driver. That git change makes it really obvious how you fix this: recompile the kernel with that change. Now, asking someone to recompile their kernel on the 2nd day they've been using Linux is just a little too sadistic for me, so I ended up SSH-ing into his computer and doing it for him. It worked! Yay!

So that all you who are stuck in this boat can get yours working too (without waiting til July), I've made a little script to automate it. Daniel Chen gave me some help because I don't understand how kernel ABIs work like he does, so thank you Dan. Here's what you do:

cd ~/Desktop
wget http://student.seas.gwu.edu/~mac/files/945correct.sh
chmod +x 945correct.sh
./945correct.sh

The first thing the script does is check to see if your hardware is affected by this bug. It will exit if the answer is no. Then it'll download the build dependencies and the source code, modify it, update the version just a bit so that Update Manager doesn't try to undo it, compile the new kernel (this part will take an hour or two depending on your machine), make debs of it, and then install those debs. Finally, it'll ask you to reboot. You don't have to reboot immediately; it simply won't go into effect until you do.

I'm not making any guarantees about this script, but the patch is known to work and worked on his computer. I turned off the "do you need this?" check and ran it on my computer without any problems. So, I think it should work for you, but if it doesn't, let me know where it screws up, OK? And pasting just "Error 2" in the comments is not enough info to debug.