Android 9.0 user debug版adb remount失败

[DESCRIPTION]

在android P版本上如果按照“FAQ18076 android 6.0 M userdebug版本执行adb remount失败”的做法在userdebug版本上执行adb remount会提示以下错误：

remount of the / superblock failed: Permission denied

remount failed

原因是android P版本后google启用avb(Android Verified Boot)2.0，verified boot and DM-verity默认启用策略发生了变化。详情如下：

DM-Verity behavior changes from vboot1.0 to avb2.0.

On vboot1.0, dm-verity is turned off on eng build and is enabled on userdebug/user build.

DM-verity could be disabled with adb (not fastboot) on userdebug build without unlocking device first.

DM-Verity could not be disabled on user build.

On avb2.0, dm-verity behavior are the same on all build variants.

It’s turned on by default and could only be disabled after device is unlocked.

dm-verity disable flag is moved from system image dm-verity metadata(vboot1.0) to vbmeta image(avb2.0), and you have two ways to disable it: adb and fastboot.

[SOLUTION]

• Android P + kernel-4.4 or kernel-3.18
  

  – download preloader with verified boot disabled which location is the same as scatter file //preloader__SBOOT_DIS.bin

– adb root

– adb disable-verity

– adb reboot

– adb root

– adb remount

• Android P + kernel-4.9 or after
  

  – download preloader with verified boot disabled which location is the same as scatter file. //preloader__SBOOT_DIS.bin
  

  – boot to Home Screen
  

  – go to setting -> system -> Developer options -> OEM unlocking
  

  – adb reboot bootloader
  

  – fastboot flashing unlock
  

  – press volume up key
  

  – fastboot reboot
  

  – adb root
  

  – adb disable-verity
  

  – adb reboot
  

  – adb root
  

  – adb remount

After Android P, preloader__SBOOT_DIS.bin will be generated automatically after building preloader.

• 请注意下载最新的adb/fastboot tool
  

  Windows
  

  https://dl.google.com/android/repository/platform-tools-latest-windows.zip
  

  Mac
  

  https://dl.google.com/android/repository/platform-tools-latest-darwin.zip
  

  Linux
  

  https://dl.google.com/android/repository/platform-tools-latest-linux.zip