Google is in the process of launching the second M preview build today. The OTA should arrive on all supported Nexus devices that have the first M build over the next few days.

For those users who just cannot wait, they can get images of the system now. The new M preview has a few important changes, but it is still a developer preview.

Some features, for instance, Now on Tap, will not work until the final release of the system. Google has released the changelog.

According to the changelog there has been a change in the wifi permissions of the system as well as the Bluetooth permissions.

There have also been permissions removed for Bookmarks and subscribed feeds.

Apps included in the system image are no longer granted dangerous permissions automatically and all of the apps should check for and request permissions at run time.

This version will also introduce the utility method which allows your app to see whether or not users have previously rejected a permission request.

This as allows for the app to explain to the user why it needs that permission. The camera permission issue that existed with Legacy Apps also has been fixed.

Google has also provided a list of the known issues that exist with the build. These include the fact that the system Messenger app crashes on the 64 bit emulator.

Contact sync experiences some issues after updating to developer preview as well. It is also currently not possible to share a video in the YouTube application.

The updated M preview will include the latest Play Services 7.6 build and the Nexus player or emulator images have been improved to make it easier to validate apps.