Can't boot following power outage

Hi, all.

I have Ubuntu 16.04 64-bit installed on an iMac5,1 (Intel Core 2 Duo T7400, 3 Gig RAM). I have installed all current updates, including the new 4.13 kernel. Note that my computer suffers from the problem described here: https://mattgadient.com/2016/07/11/l...e-2006-models/ And I initially installed Ubuntu from the image on that page. Ubuntu is installed on the hard disk directly. I have an external hard disk with OS X that boots fine. All my important data is safely backed up.

I then accidentally dropped something onto the power switch on my power outlet and the computer was suddenly powered-off.

Now the computer will not successfully boot at all. Here is a video that shows what appears on screen. https://www.icloud.com/sharedalbum/#B0s5Iy2hCP4Fv7 The same thing occurs if I select any of the 4 options on the advanced menu. I can manage to get a root shell, and I enclose a couple of screenshots that show what happens there. Note that there is a late-appearing error on of those screenshots.
IMG_0374.jpgIMG_0376.jpg
Richard

Attached Images

• IMG_0374.jpg (85.5 KB)
• IMG_0376.jpg (87.2 KB)