Articles tagged with "HTPC"

Catching a boot-time kernel oops call trace

Published on Tue 13 September 2011 under HTPC, howto

Another issue my HTPC exhibited recently was a tendency to crash early in the boot process. It became apparent it was suffering from an initialization issue in the iMon driver. I couldn't confirm it, though, since the call trace was too long to fit on the screen and it didn't turn up in any of the files under /var/log.

I studied various options for capturing the call trace, including netconsole and pstore but since I had access to an RS-232 cable with switched RX/TX pins (a.k.a. "null-modem cable"?) I ended up choosing the good old serial console. This involved connecting the HTPC to my notebook with the serial cable, starting cutecom on the notebook and doing the following on the HTPC:

sudo vi /etc/sysconfig/grub
# GRUB_CMDLINE_LINUX_DEFAULT="console=ttyS0,19200n8 console=tty0"
sudo update-grub
sudo reboot

Of course, "19200n8" must match the parameters set in cutecom on the other side of the link. With this setup, it only took a few reboots to reproduce the crash, capture the call trace and confirm the iMon driver as the culprit. Fortunately, a patch for the problem already existed so it was only a matter of either waiting until it reached my aptosid kernel or patching the kernel on my own. In the meantime, I'm booting into the previous kernel.

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