Ubuntu may be the most well-known of the Linux distributions, but that doesn’t mean much, and it certainly wasn’t enough for the operating system to reach founder Mark Shuttleworth’s ambitious goal of reaching 200 million users within four years. That was four years ago, and although it’s hard to get accurate user numbers because Ubuntu is rarely ever shipped on marketed products, most estimates suggest the operating system has an impressive number of users for a Linux distribution, but it still hasn’t even surpassed 100 million users.