Ubuntu is a free, Debian derived Linux-based operating system, available with both community and professional support.
http://ubuntu.com
Operating Systems and Servers
Get access to data on 11,466,186 websites that are Ubuntu Customers. We know of 4,430,189 live websites using Ubuntu and an additional 7,035,997 sites that used Ubuntu historically and 1,995,653 websites in the United States.
Get a list of 11,466,186 websites using Ubuntu which includes location information, hosting data, contact details, 4,430,189 currently live websites and an additional 2,256,345 domains that redirect to sites in this list. 7,035,997 sites that used this technology previously and 1,995,653 websites in the United States currently using Ubuntu.