Reboot after shutdown

[Frank Vanoni]

Hi Ubuntu users

Here is the situation:

Two brand new Dell PowerEdge T20 servers (Intel Xeon CPU E3-1225 v3 @
3.20GHz), on each a fresh install of the latests Ubuntu 16.04.1 LTS
server 16.04 (4.4.0-47-generic). 
Nothing fancy is installed, just Samba, Isc-DHCP-server and Bind.

Problem: when a "shutdown -h now" command is issued, the machine
correctly turns off (including hard discs, CPU fan, PS fan, etc.). 
About 3 seconds later, the machine restarts again.

I googled and followed the various recipes (acpi=force or acpi=noirq on
Grub, install acpid, install laptop-mode-tools, ....), unfortunately
with no joy.

What I also found out:


- If "Wake on LAN" is enabled and "USB3" is disabled on BIOS, the
machines turn off correctly. 

- If "Wake on LAN" is disabled and "USB3" is enabled on BIOS, the
machines turn off correctly. 

- If "Wake on LAN" and "USB3" are both enabled, the machines reboot
after shutdown

Weird...

Many thanks for any hint

Frank