This question already has an answer here:
Currently my Nexus 5 is on Android M preview. I know that developer preview won't get the OTA update, that's why I am trying to manually install OTA of Android M public release, but I get these errors on 50%:
failed to verify whole-file signature signature verification failed Installation aborted
adding more details:
no root no custom recovery just bootloader unlocked no changes in system files
Does manually installing Android M final release OTA work on device running on Android M preview? Or do I need to downgrade it to Lollipop first?