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.

Z8NA-D6 and lm-sensors

The ASUS Z9NA-D6 motherboard uses a w83795 chip for lm-sensors. Asus provides binary drivers, and then only for CentOS 5.4. On 5.6, you'll need these drivers. I've tested and they work on CentOS 5.6, 2.6.18-238.9.1.el5 x86_64. However, while sensors sees the chip, it doesn't manage to read the values. Must poke at it further.

Update: I finally got it working.

Disk speed

I don't know if this makes sense. In fact, I'm pretty sure it doesn't. Writing 10 GB to a WD Green 2.0TB drive in a NexStar CX USB 3.0 enclosure connected to an ASUS Z8NA-D6C.

# time dd if=/dev/zero of=/dev/sdc2 bs=1024k count=20480

20480+0 records in

20480+0 records out

21474836480 bytes (21 GB) copied, 704.374 seconds, 30.5 MB/s



real    11m44.375s

user    0m0.029s

sys     0m21.517s

Same operation on an ASUS M2N-MX SE with "only" 4 GB of RAM:

# time dd if=/dev/zero of=/dev/sdb2 bs=1024k count=20480

20480+0 records in

20480+0 records out

21474836480 bytes (21 GB) copied, 847.95 seconds, 25.3 MB/s



real    14m7.969s

user    0m0.335s

sys     7m17.540s

Mind you, Xorg is running also, so that takes up RAM and CPU.