"magic SysRq key" / System Request

https://en.wikipedia.org/wiki/Magic_SysRq_key

"magic SysRq key" / System Request

Got this by pressing alt+prntscrn+space, and copypasting from 'dmesg':

[1675314.311199] sysrq: HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(V) show-blocked-tasks(w) dump-ftrace-buffer(z)

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Configuration
The feature is controlled both by a compile-time option in the kernel configuration, CONFIG_MAGIC_SYSRQ, and a sysctl kernel parameter, kernel.sysrq.

On newer kernels (since 2.6.12[6]), it is possible to have more fine-grained control over how the magic SysRq key can be used.[7] On these machines, the number written to /proc/sys/kernel/sysrq can be 0, 1, or a number greater than 1 which is a bitmask indicating which features to allow. On Ubuntu this is set at boot time to the value defined in /etc/sysctl.d/10-magic-sysrq.conf .