I'm researching about how to create an 'update.zip' file for install the APK or APKs from Android Recovery Mode (Bootloader). I found this topic in XDA, using a script we can create the 'update.zip' file: ' ', the actual download for the script is: (updated in the page 27, comment #261).
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And here a video of how to use this simple script: But, I tried it for just a one APK (in the two ways) and the 'recovery mode' always got me 'signature verification failed'. Any idea of how to create an 'update.zip' correctly for an APK?