CyanogenMod had announced just a few hours ago its developer community was ready to roll out the first snapshots of Android 6.0.1 Marshmallow CM13 series custom ROM to smartphones and tablets.
However, users have been informed that the CM13 Release 1 series comes with some restrictions and they have to follow a particular procedure to install the new custom ROM depending on the device's current software.
Here are four scenarios on how to update the CyanogenMod firmware on the device:
If the device is running CM 12.1 snapshot (stable) or the nightly version with Googley bits, users have to install the latest Team Win Recovery Project (TWRP) firmware on the device. Only then, should they download the CM13 Release 1 firmware and the new Googley bits compatible with Android M.
Later, they should reboot the device to recovery mode and flash both the CM 13 and Googley bits. Users are warned not to reboot the device in between the installation of CM 13 and the extra package, or else it may lead to bricking of the phone.
Rebooting out of the recovery mode should be done only after the installation process is complete.
If the device is running the CM 12.1 snapshot or nightly firmware with no Google Apps, users have to install latest recovery software (either CM Recovery or TWRP) and just perform the regular recovery sortie and directly flash the new CM 13 series snapshot.
[Note (Related to Scenarios 1 and 2): If users trigger an assert violation (radio, bootloader, etc), they are advised to fulfil the requirement it complains about. These security measures are in place to ensure the firmware matches what CM13/Android 6.0.1 needs and user are able to use the device without having to worry about recurring errors.]
If the device is running CM 13 nightlies, the snapshot version should not be installed. CyanogenMod claims the new CM 13 nightlies are already running the latest codebase (Android 6.0.1_r22). So, if users attempt to install the CM13 snapshot on the device, the system will crash as it will see this as an attempted database downgrade.
If users really want to ditch the CM 13 nightlies and install the stable snapshot, they are required to perform a wipe (Dalwik wipe and Partition wipe) during the installation.
This is applicable to the Nexus 6P (angler), Nexus 5X (bullhead), Nexus 9 (flounder) smartphones and tablets only.
Depending on Scenarios 1 and 2, owners of the aforementioned devices will have to perform an additional and very important installation step.
It has been learnt that Nexus devices now ship with a large portion of their proprietary code in a vendor partition on the device itself. Since CyanogenMod cannot provide these firmware, users have to ensure their Nexus series devices are running the official software.
If not, they should go to Google's official website (HERE) and extract the latest available zip and flash the vendor image through a bootloader with "fastboot flash vendor vendor.img".
If this step is not followed, the device's vendor partition file will not match the CM build and result in error during booting due to corruption of the system and finally leading to non-functioning of device's features such as camera, and devices might get bricked in some instances.