I've got a Redhat box whose serial console (dev/ttyS0) is acting strangely. Firstly, it is echoing all input, including passwords typed at the login prompt. Secondly, running stty sane or other stty commands results in the following error:
stty: standard input: unable to perform all requested operations
When I press "Backspace" it gives me a ^H instead, and when I try to set this to erase via stty erase ^H it says: stty: missing argument to erase
so something is goofy and I'd like to be able to "reset" the serial console without rebooting. Any thoughts?
I figured out the problem. In /etc/grub.conf the kernel line contained more than one designation for console:
console=tty0 console=ttyS0,9600 console=tty0 console=ttyS0,9600n8How this second pair got in there, I don't know, but because the kernel is booted with these parameters, I can't think of any way to change them on the fly, so I edited grub.conf, removed the second pair, rebooted, and the console is behaving correctly now. I assume either (a) the presence of two conflicting console directives confused the serial port, or (b) the 9600n8 by itself was inappropriate for this console device.