Descobri isso sozinho.
sudo -H gedit /etc/fstab
deve conter
UUID="Your unique partition UUID" /prt2 ext4 defaults 0 0
/prt2/usr /usr none bind 0 0
/prt2/opt /opt none bind 0 0
/prt2/var /var none bind 0 0
/prt2/tmp /tmp none bind 0 0