ADB Remount Fails: Resolving Mount System Not in Proc Mounts Error

When using ADB (Android Debug Bridge) to modify system files on an Android device, you might encounter the error “mount: ‘system’ not in /proc/mounts.” This issue typically arises during development or customization when attempting to remount the system partition with write permissions. The error indicates that the system partition is not properly mounted, preventing write access. This is significant for users because it restricts their ability to make necessary changes to the system files, which can be crucial for development, debugging, or applying custom modifications.

Understanding the Error

The error “adb remount fails: mount system not in /proc/mounts” occurs because the system partition is not properly mounted. Here are the technical reasons and implications:

1. Mounting Issues: The system partition is not listed in /proc/mounts, which means it hasn’t been mounted correctly. This can happen due to various reasons, such as the device being in a state where the system partition is locked or protected by verified boot.

2. Read-Only State: By default, the system partition is mounted as read-only to protect the integrity of the system files. When you try to remount it with write permissions using adb remount, the command fails because the system partition is not recognized as mounted in a writable state.

3. Verified Boot: Devices with verified boot enabled require additional steps to disable verification. Commands like adb disable-verity and adb reboot are necessary to allow modifications to the system partition.

4. Root Access: Root access is often required to remount the system partition with write permissions. Without root access, the system partition remains protected, and any attempt to modify it will fail.

5. Custom Recovery: Using a custom recovery like TWRP can help in mounting the system partition with write permissions. This allows for more control over the file system and the ability to make necessary modifications.

Implications:

• Access Restrictions: Without proper mounting, you cannot access or modify system files. This restricts developers and advanced users from making necessary changes or customizations.
• System Integrity: The read-only state ensures the integrity and security of the system files, preventing unauthorized modifications that could potentially harm the device.
• Development Challenges: For developers, this error poses a challenge as it hinders the ability to test and implement changes directly on the device.

To resolve this issue, you need to ensure the system partition is properly mounted with write permissions, disable verified boot if necessary, and gain root access to the device.

Common Scenarios

Here are some common scenarios where users might encounter the “adb remount fails mount system not in proc mounts” error:

1. Development: When developers are testing apps or making changes to the system files, they might try to remount the system partition to gain write access. If the system partition isn’t properly mounted, this error can occur.

2. Custom ROM Installations: Users installing custom ROMs often need to modify the system partition. If the device’s bootloader isn’t unlocked or if the system partition isn’t mounted correctly, this error can appear.

3. System Modifications: When making modifications to the system files, such as adding or removing system apps, users might need to remount the system partition. If the device has verified boot enabled or if the system partition is busy, this error can be encountered.

4. Using Custom Recovery: While using custom recovery tools like TWRP to flash new files or make backups, users might face this error if the system partition isn’t accessible.

5. Emulator Issues: Developers using Android emulators might encounter this error if the emulator image doesn’t support write access to the system partition.

Step-by-Step Solution

Sure, here’s a detailed step-by-step guide to resolve the ‘adb remount fails mount system not in proc mounts’ error:

1. Remount the Root Partition:

   • Open a terminal or command prompt.
   • Execute the following command to remount the root partition with read-write permissions:

     adb shell mount -o rw,remount /
     

2. Disable Verification:

   • Gain root access:

     adb root
     

   • Disable Android Verified Boot (AVB) and verity:

     adb shell avbctl disable-verification
     adb disable-verity
     

   • Reboot the device to apply changes:

     adb reboot
     

3. Remount and Push Files:

   • After the device reboots, remount the system partition:

     adb root && adb remount
     

   • Push the desired files to the system partition:

     adb push <local_file> /system/<destination_path>
     

4. Using Custom Recovery Tools (e.g., TWRP):

   • Boot into custom recovery (TWRP):
     • Power off the device.
     • Boot into recovery mode (usually by holding the volume up + power button).
   • In TWRP, mount the system partition with read-write permissions:
     • Go to Mount > Select System > Mount as Read/Write.
   • Use ADB to push files while in recovery mode:

     adb push <local_file> /system/<destination_path>
     

5. Additional Tips:

   • Ensure you are using an emulator system image that is not labeled “Google Play” for root access.
   • For physical devices, using a custom recovery like TWRP can provide additional control over the file system.

By following these steps, you should be able to resolve the ‘adb remount fails mount system not in proc mounts’ error and successfully modify your system partition.

Additional Tips

Here are some additional tips and alternative methods to resolve the ‘adb remount fails mount system not in proc mounts’ error:

1. Mount the Root Partition:

   adb shell mount -o rw,remount /
   

2. Disable Verification:

   adb root
   adb shell avbctl disable-verification
   adb disable-verity
   adb reboot
   

3. Use Custom Recovery:

   • For physical devices, using a custom recovery like TWRP can provide more control over the file system.

4. Magisk Modules:

   • If you can’t mount the partition as read-write, consider using a Magisk module to replace files systemlessly.

5. Emulator System Image:

   • Ensure you are using an emulator system image that is not labeled “Google Play” for root access. Try using an Android Pie system image instead of Android Q.

6. Automated Testing Tools:

   • Tools like Repeato can help streamline the testing process by integrating ADB commands seamlessly.

If these methods don’t work, you might need to unlock the bootloader and disable verified boot.

To Resolve ‘adb remount fails mount system not in proc mounts’ Error

Follow these steps:

1. Reboot the device to apply changes.
2. Remount the system partition using ADB commands: adb root && adb remount.
3. Push files to the system partition using ADB: adb push /system/.

Alternatively, you can use custom recovery tools like TWRP to mount the system partition with read-write permissions and push files while in recovery mode.

Additional Tips

• Ensure you are using an emulator system image that is not labeled ‘Google Play’ for root access.
• Use a custom recovery like TWRP on physical devices for more control over the file system.
• Disable verification using ADB commands: adb root && adb shell avbctl disable-verification && adb disable-verity && adb reboot.
• Consider Magisk modules to replace files systemlessly if you can’t mount the partition as read-write.
• Use an Android Pie system image instead of Android Q on emulators.

Understanding and resolving this error is crucial for successful system modifications, such as pushing files or installing custom ROMs.