if you get this error when you type msfconsole:

Failed to connect to the database: could not connect to server: Connection refused
        Is the server running on host "127.0.0.1" and accepting
        TCP/IP connections on port 7175?

or your armitage does not work:

you should do:

sudo /opt/framework/postgresql/scripts/ctl.sh start
or
sudo /opt/framework3/postgresql/scripts/ctl.sh start
or 
sudo /opt/metasploit/postgresql/scripts/ctl.sh start