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Re: [Xen-users] Serial Console Problem

To: "Luke S Crawford" <lsc@xxxxxxxxx>
Subject: Re: [Xen-users] Serial Console Problem
From: "Andrew Lyon" <andrew.lyon@xxxxxxxxx>
Date: Mon, 29 Sep 2008 14:43:15 +0100
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On Sat, Sep 27, 2008 at 1:57 AM, Luke S Crawford <lsc@xxxxxxxxx> wrote:
> "Andrew Lyon" <andrew.lyon@xxxxxxxxx> writes:
>> I configured serial console on my system today by adding
>> com1=115200,8n1 console=vga,com1 to my kernel line in grub:
>> title Xen 3.2.1 / Linux 2.6.21-xen
>> root (hd0,0)
>> kernel /xen.gz vtd=1 com1=115200,8n1 console=vga,com1
>> module /vmlinuz-2.6.21-xen root=/dev/sda2
>> The xen bootup messages are logged to the serial and vga consoles, and
>> initially the kernel messages are also displayed, but it stops after
>> "Freeing unused kernel memory: 208k freed"
> it appears the problem is that you have told Xen to use the serial console, 
> but
> you have not told Linux to use the serial console... this is consistent with
> Xen outputting to the serial console, then a quiet serial console while
> linux boots, then a working getty.

You are correct, I did not tell linux about the serial console, but
some of the linux kernel messages did appear on the serial console so
I assumed that it had been auto detected, I tried adding
console=ttyS0,1152008n1 to the linux kernel parameters and that made
the serial console work correctly, but I noticed in the dmesg that the
Xen console is detected as xvc0 "console [xvc0] enabled" and there was
no ttyS0 device on which to run a getty,  so I changed the device to
xvc0 for both the kernel console and the getty and that also works.

Thanks for your help

> here is what my grub config looks like on my headless CentOS/Xen boxes:
> serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
> terminal serial console
> title CentOS (2.6.18-53.1.21.el5xen)
>        root (hd0,0)
>        kernel /boot/xen.gz-2.6.18-53.1.21.el5 dom0_mem=512M com1=115200,8n1
>        module /boot/vmlinuz-2.6.18-53.1.21.el5xen selinux=0 ro root=/dev/md0 
> console=ttyS0,115200n8
>        module /boot/initrd-2.6.18-53.1.21.el5xen.img
> the part you are missing is the console=ttyS0,115200n8   on the module line
> for the Linux kernel.   add that and I bet it will work.

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