You'll need a web server (any will do, but Apache and lighttpd can be configured automatically) and a database server, such as MySQL installed. In this guide we assume you have Apache and MySQL installed and configured. The Roundcube configuration will ask you to provide the MySQL root user's password, so have it ready.
Run the following command to install roundcube for a MySQL server:
sudo apt-get install roundcube roundcube-mysql
Configure Roundcube using the wizard that is presented to you automatically. Not all configuration options are presented at installation time, though, so once you've finished, complete the configuration with this command:
sudo dpkg-reconfigure roundcube-core
If you do not enter a name for the mail server, the user will be asked to provide one when logging in. And don't worry — it will ask you at the end if you want to restart Apache, but it will reload it, not restart it.
Roundcube is installed with English spell checking automatically. If you want to add support for another language, for instance Danish, install it with the matching Aspell package. In this example:
sudo apt-get install aspell-da
During the installation, Roundcube has automatically created and enabled an Apache configuration file. However, as it may cause problems when running multiple sites on the same server, the aliases have been commented out. To uncomment them, open up the conf file:
sudo nano /etc/apache2/conf-available/roundcube.conf
Uncomment the two aliases at the very top of the file, save (Ctrl+O), and exit (Ctrl+X).
sudo service apache2 reload
You should see no errors, unless you made a mistake in the conf file.
The Roundcube interface will now be available at <your-site>/roundcube. Notice that if you have several sites served on your Apache server using virtualhosts, all of those sites will have the Roundcube interface at /roundcube.
Log in using your full email address, the email password, and the mail server you want to connect to (if you didn't specify one during configuration) — "localhost" will do if Roundcube runs on the same hardware as your mail server.