Upgrade Ubuntu 14.10 (Utopic Unicorn) to Ubuntu 15.04 (Vivid Vervet)

Codenamed "Vivid Vervet", 15.04 continues Ubuntu’s proud tradition of integrating the latest and greatest open source technologies into a high-quality, easy-to-use Linux distribution. The team has been hard at work through this cycle, introducing new features and fixing bugs.
Under the hood, there have been updates to many core packages, including a new 3.19-based kernel, a new glibc, and much more.One of the larger changes this cycle is a switch from upstart to systemd as the default for managing boot and system service startup.

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