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To turn off my system, I can use one of these three commands:

sudo halt

Or:

sudo poweroff

Or:

sudo shutdown -h now

What are the differences between these commands, or are they all just aliases of each other?

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  • 1
    This question is marked as duplicate, but the "answers" just raise more questions - at least for those not intimate with the inner workings of Linux. On Raspbian which is still init based reboot and poweroff are links to halt. shutdown is different (the differences described in the answers). Ubuntu MATE for the Pi2 is systemd based and all 4 are links to /bin/systemctl – Milliways May 26 '15 at 0:36
76

halt terminates all processes and shuts down the cpu.

poweroff is exactly like halt, but it also turns off the unit itself (lights and everything on a PC). It sends an ACPI command to the board, then to the PSU, to cut the power.

shutdown is like poweroff, but it also runs the shutdown scripts.

Sources:

https://serverfault.com/questions/191537/shutdown-what-is-difference-between-power-off-and-halt

http://osdir.com/ml/os.solaris.managers.summaries/2001-10/msg00027.html

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