serial console speed

Jeremy Chadwick koitsu at
Thu Jul 3 15:33:29 UTC 2008

On Thu, Jul 03, 2008 at 05:34:27PM +0300, Danny Braniss wrote:
> > On Thu, Jul 03, 2008 at 03:21:14PM +0300, Danny Braniss wrote:
> > > it seems that there is no way to change the speed/baudrate of the serial
> > > console, for example, by turning it off in /etc/ttys, and running
> > > tip(1) with different speeds has no effect, it always
> > > stays at the kernel configured speed.
> > > 
> > > is this by design?
> > 
> > Yes.
> why?
> to add some more 'issues', setting 
> 	hint.sio.1.flags="0x10"
> does the redirection correctly but does not fix the speed to CONSPEED, and
> stays at 9600. (BTW, this used to work).

The 9600 limitation is out-of-the-box.  Despite what may seem logical,
in my experiences the console serial port speed on FreeBSD is "limited"
to a maximum of 9600bps unless you either use the -S flag in
/boot.config (e.g. -S115200), or loader.conf variables to adjust the

Others will have to answer your remaining questions.

> setting the serial speed means,
> 	compiling correctly btx, pxeboot, kernel, ilo.
> now it seems that any info in /boot.config or /boot/loader.conf is also
> ignored.

This part is flat out incorrect.  You no longer have to rebuild
anything, you can simply place -S115200 in /boot.config and it will
work.  I know, because every single one of our production servers
(RELENG_6 through RELENG_7) use this.  We **do not** rebuild boot

Please read this document for my findings.

| Jeremy Chadwick                                jdc at |
| Parodius Networking              |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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