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I've a home server I'm playing around with :) I want to learn server administration...
I have a hard time understanding the difference between shutdown -h now and poweroff -h now
My logic tells me it's the same thing...
But with the shutdown, Linux halts, and power stays on - I can see all lights up and cooler rotating. Strange, the only way to turn off my box completely is to use poweroff -h
Any clarification will be appreciated!
The answer is in the poweroff(8) man page:
When called with --force or when in runlevel 0 or 6, this tool invokes the reboot(2) system call itself and directly reboots the system. Otherwise this simply invokes the shutdown(8) tool with the appropriate arguments.
A bit of explanation:
The reboot() system call
is the kernel function used to reboot, halt or poweroff the
machine. It is called reboot for historical reasons, but performs
all three functions, depending on parameters that are passed to it.
The difference between halt and poweroff is that in halt mode
the control is returned to a "ROM monitor" (think BIOS), whereas
poweroff simply powers the system board off. (I have never seen
this distinction in effect on PC architectures; on Sun machines it's
different, though.)
So, when the poweroff program is invoked when the Linux system is
in runlevel 0 or 6, it will immediately power off the system via the
reboot(RB_POWEROFF) system call.
In any other case, poweroff will just behave as an alias for
shutdown now.
poweroff is just an alias for shutdown now, so it will initiate a graceful shutdown process. At the end of this process, poweroff --force is called, which actually powers the motherboard off.
Jun 23, 2021 at 13:52