Having the same problem after upgrading to from 14.10 to 15.04 on my Dell Insperion 7537. Reboot works fine, shutdown acts like reboot.
this looks like it might be related
Reboot after shutdown (Ubuntu 14.04 (also 12.04); Dell latitude E7440)
I tried
sudo apt-get update && sudo apt-get install laptop-mode-tools
and changing GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=noirq" in /etc/default/grub
also tried the entries acpi=force apm=power_off there too.
So far nothing has worked. will keep looking...
I seem to be having the same issue with Ubuntu GNOME 17.04 on an XPS 9560, even reproducing your settings/details freeze, which I hadn't though to check before. It appears to be related to the graphics interface and drivers. From exploring a variety of message boards, I see that there is a huge amount of discussion about graphics problems with Ubuntu causing lockups, in particular with the Nvidia GPU's. (I'm assuming you have one of these...if not, I'm not sure if the following would work.)
Long story short, I got my machine back into a stable state by installing the Nvidia drivers over the default nouveau graphics drivers. But even this has some caveats, which requires a bit of extra work. Below are the steps I followed and the issues that arose.
First, get the Nvidia drivers using the Software & Updates tool from the GNOME applications. Go to the Additional Drivers tab, click the "Using NVIDIA binary driver" option, and then "Apply Changes".
This will by default run the Nvidia card all the time. In principle this is fine, and I had minimal trouble shutting down and booting, though the latter takes a little longer than before. In practice, if like me you use your laptop almost all the time on battery and doing graphics non-intensive tasks, it is a bit of a power hog. Typically 20-30 W while idling, compared with < 10 W when running through the built-in Intel graphics card. (I also use TLP for power management.)
Conveniently, the Nvidia driver installation also installs a handy NVIDIA X Server Settings app that allows switching between the graphics cards, at the cost of a logout/login. Not-so-conveniently, switching to the Intel card causes the login to hang indefinitely.
So, the second-order part of this solution is to modify the kernel boot-up options as follows. (See discussion here: https://www.reddit.com/r/Dell/comments/63cavx/fixed_nvidia_1050_freezing_in_ubuntu_linux/) Edit the grub configuration file, e.g. by typing
sudo nano /etc/default/grub
into the terminal. Alter the variable GRUB_CMDLINE_LINUX_DEFAULT to
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_rev_override=1"
Save and exit (Ctrl-X). Then update grub
sudo update-grub
I find that I can now freely switch between Nvidia and Intel cards without problems (so far).
Best Answer