I read a forum post some time ago (unfortunately I don't have the link any more), that instructed me to invoke "reboot -h now" in Bash on a Raspberry Pi running the Unix-based Raspbian operating system.
It is supposed to reboot the system immediately. What caught my eye though, was the -h switch.
There is no mention in the man page for the reboot function and I can't find anything about the switch on the Internet.
Since invoking the shutdown function together with the switch -h does not throw any errors, I have to assume, that the associated daemon (I believe it's systemd) does know the switch, making me conclude that it might be a deprecated feature, which is by default ignored today since it isn't needed any longer.
I also have to mention, that since I only used Raspberry Pi's with Linux up until now, I have no idea, whether this might even be a Raspberry-specific argument.
What is that specific switch supposed to do?
It was for stopping hard disks before restarting. The reboot/poweroff/halt was instantaneous, and data could be lost. sysvinit halt.c#L16 and sysvinit htdown.c.
Nowadays, it's just ignored by systemd systemd systemctl-compat-halt.c:
case 'i':
case 'h':
/* Compatibility nops */
break;