http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=404497
Consider the session below: $ stty -F /dev/ttyS0 9600 $ stty -F /dev/ttyS0 -g > stty.ttyS0.txt $ stty -F /dev/ttyS0 115200 $ stty -F /dev/ttyS0 `cat stty.ttyS0.txt` stty: /dev/ttyS0: unable to perform all requested operations $ stty -F /dev/ttyS0 `cat stty.ttyS0.txt` $ As far as I can tell, the (bogus) error message is due to the stty's ignorance of c_ispeed and c_ospeed fields of struct termios.