Re: Serial console baudrate
From: tns1 (tns1_at_cox.net)
Date: 09/13/03
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Date: Sat, 13 Sep 2003 08:18:26 -0700
>>During bootup, the baudrate for this port changes at least 3
>>times. The bios sets it to 19200 which lasts from powerup thru
>>the grub menu, and up until the kernel image is loaded. Once
>>the kernel starts, the baud rate is changed to 9600 which
>>lasts thru the kernel & network setup until just before the
>>login prompt. At this point, the baud setting in inittab is
>>applied.
>
>
> You can specify the baud rate to be used in all three phases:
> grub, kernel, getty. I recommend setting them all the same. I
> usually use 115200 baud.
>
I'll change what I can, but there is no way to change the baud rate
selected by bios, so I either match everything to 19200, or live with
not seeing the bios screen.
> Read the "remote serial console howto" at www.tldp.org:
> http://www.tldp.org/HOWTO/Remote-Serial-Console-HOWTO/
I'll have to play with the grub settings.
>
>>Now when I do #reboot , it looks like the baud rate is again
>>changed since there are some messages missing that I normally
>>see on a crt. Can anyone verify these different baud rate
>>regions?
>
> I don't understand the question.
>
On the serial console, I just see the 'rebooting now!' message, yet on
the regular console, I will see three or four more messages having to do
with halting, and cleaning up log files. My guess is that the kernel has
once again changed the baud back to 9600 just before shutdown. Maybe
this is all normal and forseeable if you understand the mechanics of it
all, but I expected the getty settings to remain until shutdown.
I realize I won't always see output on the serial console for certain
rate mismatches, so have I missed some other players in this 'musical
chairs' baud rate game?
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