Sorry for the lay question, but does this mean you’re unmounting your primary drive and powering off your system, as opposed to the shutdown (graceful) and poweroff (less graceful) shell commands?
It's a way of sending commands to safely power down a linux (maybe *nix?) system even when it is in an otherwise unresponsive state -- I'm pretty sure not a kernel panic, but if it's otherwise frozen, these [0] may work.
The current usual advice
for a safe shutdown is REISUB, with the mnemonic 'Reboot Even If System Utterly Broken', but the old mnemonic a lot of folks will still know is 'Raising Skinny Elephants Is Utterly Boring'. It seems to have been replaced because it flushes data to disk earlier in the sequence than killing off processes, potentially leaving data from running processes un-flushed.
