Wubi is an installation method helps users install Ubuntu/Xubuntu alongside with Windows as an application (It creates a huge file to contain X/Ubuntu).
However, it has this problems: cannot boot to Ubuntu after update or cannot boot at all. The errors is “could not mount” some partitions,etc.
To boot to inside Ubunt in this case, we select “e” to edit the boot parametes, and see something like this
loop=/ubuntu/disks/root.disk ro rootflags=sync quiet splash
change the “ro” (read-0nly) to “rw” then press F10 to continue booting process.
After that, open /etc/grub.d/10_lupin and change aall “ro” to “rw”.