Since last week shutdown has stopped working in my system. Either i use the shutdown menu in Unity/LightDM or use sudo shutdown -h now the system just locks, and i can't either use Alt+reisub. Only a hard shutdown works.

If i shutdown from a tty, this is the last output i get before the system freezes:

umount: /run/lock: not munted

umount: /run/shm: not mounted

mount: / is busy

* Will now halt

[...] Power down.

After this the disk usage led turns on and i can't do anything else.

What could be the problem?

What i have tried

• set acpi=force in GRUB doesn't help;


• check for errors in the shutdown process: i get any error at all during shutdown, except the lines stated on top;


• acpid is installed.


• reboot/suspend works just fine!

Edit

As seen here i get some warnings regarding ACPI in /var/log/boot.log.