CPUs are computers

So I wanted to get a Shuttle DX30 working under LTSP. First step, it uses a pxe-client-id that's 9 bytes long. CentOS's dhcpd throws away anything that doesn't have a 17 byte pxe-client-id. I have no idea why. I tried poking around the RFCs but didn't find much of interest.

Once I patched dhcped, PXE booting worked and I managed to load a kernel. Except it was slow.

Very.

Very.

Very.

Slow.

Just how slow? It took over 30 minutes to get to a XDM prompt slow.

I saw Machine check events going past. To track those down, I put my laptop's 2.5 inch HDD into it. This was also slow. While not as bad, it was clearly not working properly. But I got mcelog to grab the following:

mcelog: failed to prefill DIMM database from DMI data
mcelog: mcelog read: No such device
Hardware event. This is not a software error.
MCE 0
CPU 0 BANK 4 
ADDR fef5d200 
TIME 1531800239 Tue Jul 17 00:03:59 2018
MCG status:
MCi status:
Error overflow
Uncorrected error
MCi_ADDR register valid
Processor context corrupt
MCA: Internal unclassified error: 408
Running trigger `unknown-error-trigger'
STATUS e600000000020408 MCGSTATUS 0
MCGCAP c07 APICID 0 SOCKETID 0 
CPUID Vendor Intel Family 6 Model 92

After some messing around, cursing the Gods, discussing Intel NUCs on #ltsp, general lack of sleep, I found the solution : kernel-ml

yum -y  --enablerepo=elrepo-kernel install kernel-ml
joe /etc/grub.conf # set default=0

It should be noted it took over 10 minutes for dracut to create the initrd for kernel-ml. But once I then booted into the new kernel, everything was fine. I installed kernel-lt as a test, because it needs the CPU and the disk to run smoothly and it took 2 minutes, which is annoying but expected. For reference, installing kernel-ml on my desktop takes 1.5 minutes but it has an SSD.

kernel-lt was a failure, 9m54 to install kernel-ml-4.17.5-1.el6.elrepo.x86_64. I booted back into kernel-ml, removed and reinstalled kernel-ml-4.17.5-1.el6.elrepo.x86_64 and it took 1m52. So kernel-ml is the clear winner.

Now to find out how to install kernel-ml into LTSP.

CentOS5 and a recent kernel.

CentOS 6 is just around the corner. But for those of us who have CentOS 5 deployed just about everywhere, the wait for a better kernel is annoying. While wasting time in some unsavoury corner of the Internet, I came across vserver, which is a clever way of sharing a kernel between separate OS instances. Think of it as VM writ small.

But even if you don't want or need multiple OSes, vserver installs a RHEL 6 kernel. And it works with CentOS 5. Say you need ATA TRIM? You got it. Having trouble getting WiFi working? Bingo. Card reader on your Laptop not working? It does now.

EDIT: the catch is that sound is no longer working. While this is OK for the laptop, it isn't for my desktop. Ah well.

However, I can TRIM corey's SSD by booting with the vserver kernel, then doing

dd if=/dev/zero of=/tmp/very-large

rm /tmp/very-large

The first command is going to fill any remaining space on the disk with zeros, so don't be doing anything important at the same time. When the disk fills up, it will exit and the second command will free the space.

You could also do the same thing with any boot CD that has TRIM support.

Silence!

Newegg.ca sent me email yesterday with a tracking number. Click on it and BUH "we have no information about this package." Yes, you are idiots.

But this morning, I try again at 8h00. And BUH PACKAGE ON TRUCK IN SHERBROOKE!

So I don't go back to bed, wait impatiently for the truck to show up. Three cheers for eCommerce!