Everything is working fine after installing the Opengeo Suite in Ubuntu except PostGIS issues. In the dashboard the PostGIS manage is disabled(grey) but PostgreSQL is working via pgadmin3. And also when we create a new database the tables "Geometry Columns" & "Spatial Ref_System" isn't getting created. Also we are not able to import any shape files.
"On Linux installations the postgis specific functionality on the dashboard is explicitly disabled since it's not running as a native app." (see No Postgis after installing opengeo suite).
To import shape files have a look at the documentation or explain your problem in more detail.
Moreover, note that the OpenGeo is officially supported only for Ubuntu 10.04, however it is reported to work well also under 12.10. I had troubles with 13.04 myself, see GeoServer Web Admin Interface: 404 error.