Problem solved: Ubuntu boots up with only terminal

It could happen to Ubuntu that it boots up with a command line terminal only and the gnome desktop can not load correctly, typically after some update of the system and the culprit might be the failure of the initialization of some hardwares.

To this end, we need a wired network connection since the wireless network can not load before the desktop boot-up. The following command solves the trouble.

# apt-get install gnome-core