I thought I would share how I avoided that message from showing up.
I was installing Ubuntu 14.04 into a VirtualBox virtual machine on Windows 8 64-bit. I used Ubuntu 14.04 AMD64 ISO file which is what the Ubuntu download page automatically selected for me. Installation was going well until one moment when it got stuck with the following message:
Running post-installation trigger update-notifier-common
I searched for the message on Google and the first result said that it could happen if the machine enters sleep during installation.
So I tried again except this time ensuring that I move my mouse around occasionally. Is “occasionally” the right word? It again got stuck with the same message.
My two tries were done on a laptop connected to the Internet by tethering to my phone. Then I remembered that the tethered Internet connection can get unstable sometimes.
So I tried again but this time the laptop was connected to a stable and fast Wi-Fi and the installation succeeded.
Ubuntu in VirtualBox seems to work fine. I was worried that it might be slow because I heard that there is some issues between Ubuntu Unity and VirtualBox and because I don’t see virtual machine optimization BIOS settings on my laptop, but it isn’t slow (as long as you enable 3D acceleration, which is not enabled by default.).
I noticed that Ubuntu in VirtualBox on Windows 8 might be usable even without physical keyboard. So I can detach the detachable keyboard from the laptop and carry only the tablet around and start the virtual Ubuntu on it when necessary. Keyboard input can be emulated by Windows 8 touch keyboard and mouse input can be emulated by touch. Left click and right click can be emulated by touch. Middle click on the other hand, for that you need Autohotkey. So that’s a tablet carrying Ubuntu Desktop.