“bus error” when trying to reboot Linux-Collection of common programming errors
What does the end of dmesg output?
From the description is sounds like you may have a serious hardware issue that will prevent you from being able to reboot, as the commends you’ve given should have done the job for you already.
Otherwise the only think I know of is issuing commands directly to init using telinit, but I thought that that was what shutdown and reboot both basically did anyway.