this is correct steps:
sudo apt-get install postgresql-9.3 postgresql-contrib-9.3 postgresql-server-dev-9.3 pgadmin3
if needed install extension new postgres9.3
Check 2 clusters
sudo pg_lsclusters
Stop all services
sudo service postgresql stop
drop default main cluster 9.3
sudo pg_dropcluster --stop 9.3 main
Start upgrade!
sudo pg_upgradecluster 9.1 main
Drop old 9.1 server
pg_dropcluster --stop 9.1 main
Start server
sudo service postgresql start 9.3
Servizieinformatica 