Shutdown/Reboot hangs Indefinitely - Ubuntu 16.04

Solution 1:

I got exactly the same problem on Ubuntu 16.04 LTS. After installing amdgpu-pro drivers ver. 492261 system hangs at reboot. Last message printed is: Restarting System

I solved the issue by adding reboot=pci to the list of parameters passed to the kernel:

• Edit /etc/default/grub
• Add reboot=pci to the end of GRUB_CMDLINE_LINUX_DEFAULT variable
• run as root: update-grub
• reboot (system will hang, turn off/on manually)
• reboot (this time it will work)

I tried all the suggestions in the other answers and they didn't solve the issue for me.

Solution 2:

The problem occurred when the PCI device controlled by the mei_me module was with Runtime Power Management activated.

I got it fixed by adding mei_me module to the RUNTIME_PM_DRIVER_BLACKLIST configuration of TLP.

So, If you have this same problem. It's probably some PCI device with Power Management issues..

Solution 3:

I had a similar issue running Ubuntu Server 16.04LTS on Vmware. On shutdown it would "hang" for some time and then proceed to shutdown or reboot. Turns out my host was not configured to do NTP sync, while ubuntu does by default. The host clock was out. As soon as I let the host sync too problem disappeared.