Every time I select Ubuntu 12.04 when booting my HP 540 laptop, the machine restarts. How can I fix this, so I can successfully boot my Ubuntu system?
I had the same problem with my Toshiba laptop. After some investigation, it seems that the "wake up on lid being open" is enabled and, of course, the lid is open just after it shuts down. A workround for this is:
sudo echo LID > /proc/acpi/wakeup
This can be put in