Avoiding Screen Pollution from Kernel Messges
Don't you just hate it when kernel messages pollute your display in the form of those annoying black rectangles overlaid above whatever you're working on? This is a known bug in rio(1); for further detail, see Rob Pike's message to this effect.
To work around this problem, open a new terminal window and do:
This works because, according to the kprint discussion in cons(3), "if (the) console is a graphics screen, the data is sent either to the display or to kprint, but not both."
Another more permanent solution to the problem is to put
cat /dev/kprint >/dev/null >[2=1]
somewhere in termrc (see cpurc(8)).