Stumbled across this today while searching for a fix for a PC running 16.04 that this is happening on. I don't understand why, but editing /etc/default/grub to uncomment the line for graphical terminal fixed it. What that has to do with mounting root I don't know, but that was certainly the fix.
I noticed that I could hold shift and select the same kernel, with the same command line options, under the advanced menu and get the system to boot. Uncommenting #GRUB_TERMINAL=console fixed it.
Stumbled across this today while searching for a fix for a PC running 16.04 that this is happening on. I don't understand why, but editing /etc/default/grub to uncomment the line for graphical terminal fixed it. What that has to do with mounting root I don't know, but that was certainly the fix.
I noticed that I could hold shift and select the same kernel, with the same command line options, under the advanced menu and get the system to boot. Uncommenting #GRUB_TERMINAL= console fixed it.