How to install metasploit on ubuntu:

1. Download metasploit for linux at http://www.rapid7.com/products/metasploit/download.jsp

2. Make the file executable.

For 64-bit systems:
chmod +x metasploit-latest-linux-x64-installer.run
For 32-bit systems:
chmod +x metasploit-latest-linux-x32-installer.run

3. Run the installer.

For 64-bit systems:
./metasploit-latest-linux-x64-installer.run
For 32-bit systems:
./metasploit-latest-linux-x32-installer.run

4. Follow the wizard installation instructions.

5. Start metasploit

By commandline: msfconsole

By browser: https://localhost:3790