I've got a system with both serial and USB keyboard attached, and I would like to get into ddb after the system has booted (to single-user mode). I've verified that ddb.fromconsole is set and I've used hw.cnmagic to create a keystroke sequence "QQ" (0x51 0x51) but it does not get me into ddb. I dealt with a system that had two usb keyboards but the second one was real (first on a DELL drac somehow). We ended up kludging the usb console code to just use the second one. I dimly recall that there is some notion of a "this is the console" flag and it only gets set on one device. You didn't say, but presumably your QQ sequence does not work on either the USB keyboard or the ps/2 keyboard (or is your console a real serial port?). On a netbsd-5 system with only usb keyboard, ctrl-alt-esc drops into ddb, at least when not running X (didn't try with X).
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