4 ms·

echo o > /proc/sysrq-trigger will shutdown a AWS instance immediately. I've used it a couple of times to make real sure my costly spot instance was terminated.

• derefr 6y ago
  https://elixir.bootlin.com/linux/latest/source/kernel/power/poweroff.c#L21 https://elixir.bootlin.com/linux/latest/source/kernel/power/... Looks like SysRq-o does a clean poweroff, not a dirty/immediate one — it calls kernel_power_off(), not machine_power_off(). This means, importantly, that can actually take some time to happen, as drivers get a chance to run deinitialization code. This also means that a wedged driver that doesn't respond during deinit can prevent the kernel from halting. Thus, while SysRq-o might be useful for killing a wedged userland, it's not a panacea — especially, it isn't guaranteed to complete a shutdown for unstable kernels, or kernels with badly-written DKMS drivers attached. It's not truly equivalent to a power-cut.