As you may know, Canonical has created a special Ubuntu Snappy Core image for the Raspberry Pi 2 ARM mini computer, to help the users familiarize with Ubuntu for the Internet of Things OS.
Canonical has created a second Snappy Ubuntu Core 15.04 for the Raspberry Pi 2 and advices the users to re-flash their devices, an over-the-air update not being available. The new image brings a new kernel (kernel 3.19), permits the users to roll back updates and to receive ubuntu-core rootfs.
As you may know, the Internet of Things (or IoT) is a concept that aims to connect all the devices running an operating system.
The latest Ubuntu Snappy Core 15.04 image for Raspberry Pi 2 can be downloaded from people.canonical.com/~platform/snappy/raspberrypi2/.