Use the command keys
For instance to panic the system or show backtrace of the CPU(s)
To show backtraces:
# echo l > /proc/sysrq-trigger
# dmesg
To panic the system:
# echo c > /proc/sysrq-trigger
All available options:
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)