Re: [Xen-users] inittab corrupted/serial console broken on Xen-ified kernel?

[Tom Brown <xensource.com@xxxxxxxxxxxxxxxxxxx>]

On Mon, 17 Dec 2007, Evan Lavelle wrote:

> David Stone wrote:
> >  Here's what I do on an F7 system with a built Xen 3.2 and Xenified
> >  Linux kernel from the Xen soure: (2.6.18):
> >
> >    Add the folloing line to /etc/inittab (after the rest of the getty
> >    lines)
> >      s1:12345:respawn:/sbin/agetty -L 115200 ttyS0 vt100
> >    Add "ttyS0" to /etc/securetty
> >    (Reboot)
> >    For Xen/Dom0:
> >      On Xen "command line" (in grub.conf) add: com1=115200,8n1
> >      On Xenified Linux "command line" (in grub.conf) add: console=ttyS0,
> >      115200
> >
> >  It works for me no problem...it looks like you're doing more or less
> >  the same thing?
> Yes, looks pretty much the same:
>
> grub.conf:
>  kernel /xen.gz-2.6.21-2952.fc8 com1=115200,8n1
aren't you missing the console=com1 part of the above line? Without that I 
think you're likely to be screwed. You're not telling XEN to grab the 
serial port, and the default XENified kernels don't usually have "real" 
serial port drivers in them... at least they didn't used to.... what is 
confusing is that your dmesg output from 
http://lists.xensource.com/archives/html/xen-users/2007-12/msg00486.html
shows ttyS1 ... but NO ttyS0, which pretty much explains why agetty can't 
open it and keeps exiting... causing init to whine about it respawning too 
fast. (but without serial drivers, I wouldn't have expected to see a 
ttyS1, which is confusing the daylights out of me.)
you might try using mgetty instead of agetty, it has better logging 
(better everything except size and simplicity:). You can also try a simple
    echo testing > /dev/ttyS0

and see if that generates output or a "no such device" error.

>  module /vmlinuz-2.6.21-2952.fc8xen ro root=/dev/VolGroup00/LogVol01 
> rhgb quiet console=ttyS0,115200n81
> inittab:
> co:12345:respawn:/sbin/agetty ttyS0 115200 vt100
<snip>

I've got several pairs of xen machines, where each is connected to the 
console of the other. AFAIK that doesn't work with the default xen linux 
kernel builds, due to the missing serial drivers. Basically XEN replaces 
the serial layer so it can provide a fake serial console that knows about 
the hypervisor... at least it used to. It would be really nice if the 
situation has improved to the point where the hypervisor and linux can 
both dump console output on one serial port, and you can actually use a 
different serial port with minicom. (Maybe that's what xvc0 is about!?) In 
my experience, you need to custom compile a kernel, and NOT give XEN the 
console=com1 parameter to let the linux console run on ttyS0 and be able 
to access ttyS1 from minicom ... but AFAIK, that is rambling and not 
related to your question.
-Tom



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