I am having instances of UML "crash", only to assume that there wasn't enough virtual memory (and/or swap).

When restoring the screen session, I see kernel details outlining virtual pages and such (I am not as UML literate as you are unfortunately), but it is "frozen", i.e. no CTRL+C/D will do anything. Is there some combination where you can forcefully [halt]/[reboot]/[drop to a shell] the kernel?

Many Thanks for your time,