Updating Raspberry Pi
The Raspberry Pi essentially has three software layers: the closed source GPU boot process, the boot loader (also known as the firmware), and the operating system. At the time of writing book, we cannot update the GPU code. But maybe, one day, Broadcom or hardware hackers will tell us how do to this.
This leaves us with the firmware and the operating system packages. Broadcom releases regular updates for the firmware as precompiled binaries to the Raspberry Pi Foundation, which then releases them to the public. The Foundation and other community members work on Raspbian, and release updates via the aptitude repository; this is where we get all our wonderful applications from.
It is essential to keep both the firmware and the packages up to date so that you can benefit from bug fixes and new or improved functionality from the Broadcom chip.
Raspberry Pi 2 uses ARMv7 as opposed to Pi 1, which uses ARMv6. It is recommended to use the latest version of the Raspbian release...