Len Brown wrote:
Do you have a second computer around with a serial port ? If yes, then
please add the following to the kernel command line:
earlyprintk=serial,ttyS0,115200 apic=debug
and connect the serial ports with a null modem cable. Fire up a
terminal program on the second machine and capture the output.
I do have a second computer, and went out and bought a null modem adapter for
my serial cable and connected the two machines. I've tried installing minicom
and also connecting it to ttyS0 at 115200 baud on the second machine, but when
I boot the first machine I don't see any output on the terminal.
/boot/grub/menu.lst:
serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
terminal --timeout=300 serial console
is what I use.
this will give you a prompt from grub even before the kernel boots
so you can select (and edit) your kernel via menu over the serial line
if you wish.
I've got that working now. I used minicom on the remote machine,
capturing the output. You can see me fumbling around, editing the
kernel command and booting here:
http://intertwingly.net/stories/2009/02/09/minicom.out
While it is difficult to make out what I did given line wrapping, etc,
what I started with was:
/boot/vmlinuz-2.6.27-11-generic
root=UUID=4fce230e-fe72-4685-aab0-294ef1c20efa ro noapic quiet splash
After editing, what I had was
/boot/vmlinuz-2.6.27-11-generic
root=UUID=4fce230e-fe72-4685-aab0-294ef1c20efa ro quiet splash
earlyprintk=serial,ttyS0,115200 apic=debug
As you can see, the last line I saw was "Starting up ...", after which
point the "MP-BIOS bug: 8254 timer not connected to IO-APIC" etc output
appeared on the monitor that is directly connected to the machine being
booted (i.e., this text did not appear on the minicom session).
If this doesn't work, then the kernel earlyprintk is unlikely to work
also.
At the moment, it looks like it works, but earlyprintk does not work for
me, at least not on Ubuntu 8.10, kernel 2.6.27-11-generic.
Note that there may be some BIOS SETUP options related to the serial port
-- worth checking.
Also, in minicom, be sure to turn off HW flow control
there is a fancy serial console document someplace on this,
probably at http://tldp.org/
As I have managed to get grub to talk to the serial console, I did not
explore these options further. Please let me know if there is something
in particular I should explore.
good luck,
-Len
- Sam Ruby
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