ubuntu *sometimes* restarts when i try to shutdown (shutdown -P now, halt, init 0)

Question

I have had ubuntu running fine from usb external hd. When i bought a new laptop (toshiba L775D-S7222) and tried to boot I found that not always but sometimes there was a problem that shutdown did not poweroff rather restarted. Also when this happens my laptop keyboard and mouse dont work at all and I need to use external. When this happens I sometimes fing in the bios that internal mouse is disabled even though I know clearly that I left it enabled.

How can I go about debugging this?

some lines from dmesg:

[    2.770728] ehci_hcd 0000:00:16.2: QUIRK: Enable exception for AMD Hudson ASPM
[    2.770741] ehci_hcd 0000:00:16.2: applying AMD SB700/SB800/Hudson-2/3 EHCI dummy qh workaround
[    3.011495] powernow-k8: Found 1 AMD A6-3400M APU with Radeon(tm) HD Graphics (4 cpu cores) (version 2.20.00)

thanks

Answer 1

Not sure why it would restart, but halting is not the same as powering off. However, upstart actually confused things quite a bit by powering off when one called halt. Note that this bug was fixed in Ubuntu 11.10:

https://bugs.launchpad.net/ubuntu/+source/upstart/+bug/532366

However, I'd suspect that if halt issued an ACPI power off command, and instead ended up rebooting the machine, that sounds like maybe a kernel problem or BIOS incompatibility.