After upgrading a Ubuntu server from Karmic Koala (9.10) to Lucid Lynx (10.04) reboots would result in the following error “An error occurred while mounting /proc/bus/usb Press S to skip mounting or M for manual recovery.” Selecting the skip option the server would continue to boot.

As you can imagine this problem while not show stopping can cause head banging against wall moments if a remote reboot is performed. So I eventually got around to investigating the root cause.

It turns out that VirtualBox was the culprit. The following line in “/etc/fstab” was once required to get USB support in the VirtualBox guests: “none /proc/bus/usb usbfs devgid=125,devmode=664 0 0” . Removing this entry solved the reboot issue and my saved my head from serious damage.