While installing ubuntu 12.10, when i got to the partition-ing part, i kept on receiving an error saying something like “no root file system is defined.” After countless attempts, i figured out a solution to this.
Firstly, make sure that the partition where you are installing ubuntu is an ext4 partition, and dont leave _mount point _empty. To do so, just double click the partition, and in the box that pops up, select the ext4 journalling file system, and in mount point, just add a single “/”
That’s it! you should be able to proceed now.