cu -l /dev/nmdm not setting rows and columns

Craig Rodrigues rodrigc at
Wed Nov 26 23:34:12 UTC 2014

On Sun, Nov 23, 2014 at 6:04 PM, Peter Grehan <grehan at> wrote:

> Hi Craig,
>  # stty -a
>> speed 9600 baud; 0 rows; 0 columns;
>> # echo $TERM
>> dialup
>> Any idea how I can fix this?  The console inside the VM
>> is quite unusable when it does not have the correct
>> rows/colums set.
>  Not sure how you're getting 'dialup' as the terminal type: the default
> ttys file for 10.1 shouldn't need to be edited, and has
> ttyu0   "/usr/libexec/getty std.9600"   vt100   onifconsole secure
>  The rows/columns is always 0 for uart-style serial lines since it's not
> possible to know what's on the other end. That's why $TERM has to be set
> correctly for these.
>  Having an xterm attached to the other end of an nmdm device isn't too
> different from swapping say a vt100 with a vt420 or some other terminal
> with a different resolution on a real serial line. There's no way for the
> serial driver to know this has happened.
>  The only way to fix the changing-size problem is to have a
> paravirtualized tty device that has a way of reading the terminal window
> size and being informed of changes. The virtio-serial specification has
> this ability, however, the FreeBSD driver for this can't operate in polled
> mode so can't be the main console port, and in any event there's no bhyve
> backend for it currently.
>  Or, you can network-login to the guest in which case xterm works fine :)


I need to log into the serial console for two reasons:
   -> networking has not been set up yet, and I need to log in to see what
is going on
   -> networking has failed or been misconfigured, so I cannot ssh into the
VM, but I still need to log in to see what is going on

cu and tip are in the base system, so they are handy to use, but they are
quite primitive.
Do programs like minicom work better for this type of thing, in terms of
a usable terminal?  I haven't used these types
of programs for serial port communication since the 1990's, so it's been a
while for me.


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