@Garp you should login as nemo, not root. password set in developer mode settings. to gain root you should use devel-su later.
"ssh -i my_n9_identity root@192.168.2.15"
Just deleting earlier long story just telling: To get root access in Ubuntu 12.04 (and maybe even 13.10?) in Ubiboot maintenance mode N9, just in Ubuntu Alt-F2 and key-in gksu nautilus then you have root access to all of it!