A few days ago, I was browsing questions on
Mathematics Stack Exchange on Ubuntu 14.04 LTS. I opened
lots of tabs in Google Chromium. Suddenly, the screen
went grey. I don’t know the cause. I hadn’t seen such problem
before. I waited for about one minute, and I switched to the terminal
tty3. The grey screen became black without any text. I pressed
<Ctrl>-<Alt>-<F7>, then the monitor showed the grey screen again.
I looked at the light (not the power button) in the desktop. I
thought it represented the hard disk activity. Its blinking was
normal. As a result, I guessed the problem was related to the
display. I pretended I could normally see things, and I imagined
the picture. I logged on
tty3 without logging off
tty7. Then I
sudo reboot and supplied the password. Within several
seconds, I heard a beep sound and the system rebooted.
Certainly, all unsaved works on
tty7 had been lost. Therefore, it
was very important to save your work. As I’m no longer an IT worker,
I won’t try to find a solution after reading a few related posts
which I have difficulty to understand. Within six months, a new LTS
version of Ubuntu will be launched. The price of a SSD will drop, so
perhaps I will clean install Ubuntu on a SSD.