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.
Ubuntu Desktop has seen incremental improvements, with newer versions of GTK and Qt, updates to major packages like Firefox and LibreOffice, and stability improvements to Unity.
Ubuntu Server 15.04 includes the Kilo release of OpenStack, alongside deployment and management tools that save devops teams time when deploying distributed applications - whether on private clouds, public clouds, x86 or ARM servers, or on developer laptops. Several key server technologies, from MAAS to Ceph, have been updated to new upstream versions with a variety of new features.
This release also includes the first release of snappy Ubuntu Core, a new distribution model based on transactional updates.

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Ubuntu Server is a full-featured Linux distribution for desktops, laptops, netbooks and servers, with a fast and easy installation and regular releases. A tightly-integrated selection of excellent applications is included, and an incredible variety of add-on software is just a few clicks away.