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.