Well windows serial and linux serial are totally different beasts.
I'd suggest you start off having a shell window open on your linux host and do a "tail -f /var/log/syslog" before you start the IDE or connect your Uno. Then connect the uno to see what the OS says is going on, then start the IDE and select your board and serial port and then go through the remainder of steps to reproduce the problem. you should not see additional messages about the uno/usb tty disconnecting. If you do, take the syslog messages and post them here.