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A freshly built machine running Ubuntu 12.10 64bit is hanging under seemingly random conditions. To debug this I've installed linux-crashdump, confirmed that the second kernel is loaded and a simulated crash creates files under /var/crash. However, the real crash does not trigger the crashdump system, no auto-reboot happens and no dump are written out.

Are there some hints about the cause I could glean from the hang not triggering the system? Could something hang a machine in a similar way to a kernel panic?

Normally I'd just strip the machine down to a minimum config and work my way up from there but due to a cramped chassis this would involve re-attaching the CPU cooler a few too many times to my liking. No serial port to dump to console either.

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What kind of hang? Is networking still up? Do the CapsLock and other keyboard LEDs react? If so, perhaps just X crashed/locked up. If the machine just turns off after running a while, it is most often CPU overheating. – vonbrand Mar 4 '13 at 17:37

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