Bind
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www.miodominio.com IN CNAME miodominio.com
Nota: non dimenticare i punti!
Apache2
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in /etc/apache2/sites-available/miodominio.conf:
DocumentRoot /home/sito/www
ServerName miodominio.com
<Directory "/home/sito/www">
allow from all
Options +Indexes
</Directory>
ServerAlias www.miodominio.com