Android O, Failed To Mount /system, /dev/block/dm-0 Is Read Only

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Introduction

Android O, also known as Android 8.0 Oreo, is a significant update to the Android operating system. It brings several new features and improvements, including a new file system layout and a more secure boot process. However, with these changes come new challenges, and one of the most common issues users face is the inability to mount the /system partition in read-write mode. In this article, we will explore the reasons behind this issue and provide a step-by-step guide on how to resolve it.

Understanding the Issue

When you try to mount the /system partition in read-write mode using the command mount -o rw,remount /system, you may encounter an error message indicating that /dev/block/dm-0 is read-only. This error can be frustrating, especially if you need to make changes to the system files. To understand the issue, let's first look at the file system layout in Android O.

File System Layout in Android O

In Android O, the file system layout has changed significantly. The system files are now stored on a separate partition, which is mounted as /system. This partition is read-only by default, and any changes made to it require a remount operation. The /dev/block/dm-0 device is a block device that represents the system partition. When you try to remount the system partition in read-write mode, the system checks the permissions of the /dev/block/dm-0 device. If the device is read-only, the remount operation fails.

Why is /dev/block/dm-0 Read-Only?

There are several reasons why the /dev/block/dm-0 device may be read-only. Here are a few possible causes:

  • Secure Boot: Android O introduces a new secure boot process, which requires the system partition to be read-only during boot. This ensures that the system files are not modified during the boot process.
  • Read-Only File System: The system partition in Android O is mounted as a read-only file system by default. This is done to prevent accidental modifications to the system files.
  • Device Permissions: The permissions of the /dev/block/dm-0 device may be set to read-only, preventing any modifications to the system partition.

Resolving the Issue

To resolve the issue, you need to remount the system partition in read-write mode. Here are the steps to follow:

Step 1: Check the Device Permissions

First, check the permissions of the /dev/block/dm-0 device using the ls -l command:

ls -l /dev/block/dm-0

If the device is read-only, you will see a permission string indicating that the device is read-only.

Step 2: Remount the System Partition

To remount the system partition in read-write mode, use the following command:

mount -o rw,remount /system

If the device is read-only, you will see an error message indicating that the remount operation failed.

Step 3: Check the Secure Boot Status

If the secure boot status is enabled, you will need to disable it before remounting the system partition. To check the secure boot status, use the following command:

getprop ro.boot.secure

If the secure boot status is enabled, you will see a value of 1. To disable secure boot, use the following command:

setprop ro.boot.secure 0

Step 4: Remount the System Partition Again

After disabling secure boot, remount the system partition in read-write mode using the following command:

mount -o rw,remount /system

This time, the remount operation should succeed, and you should be able to make changes to the system files.

Conclusion

In conclusion, the /dev/block/dm-0 device is read-only in Android O due to the secure boot process and read-only file system layout. To resolve the issue, you need to remount the system partition in read-write mode by disabling secure boot and checking the device permissions. By following the steps outlined in this article, you should be able to resolve the issue and make changes to the system files.

Additional Tips

Here are some additional tips to help you resolve the issue:

  • Use the adb shell command: If you are using the adb command-line tool, use the adb shell command to access the Android shell and execute the remount command.
  • Check the system logs: Check the system logs to see if there are any error messages indicating the cause of the issue.
  • Use a file system editor: Use a file system editor, such as adb shell or busybox, to edit the system files and make changes to the system partition.

Related Articles

Here are some related articles that may help you resolve the issue:

  • Android O: Secure Boot and Read-Only File System
  • Android O: Remounting the System Partition
  • Android O: Troubleshooting Common Issues

References

Here are some references that may help you resolve the issue:

  • Android O: Developer Documentation
  • Android O: System File System Layout
  • Android O: Secure Boot and Read-Only File System
    Android O, Failed to Mount /system: /dev/block/dm-0 is Read Only - Q&A ====================================================================

Introduction

In our previous article, we explored the reasons behind the issue of /dev/block/dm-0 being read-only in Android O, and provided a step-by-step guide on how to resolve it. However, we understand that some users may still have questions and concerns about this issue. In this article, we will address some of the most frequently asked questions (FAQs) related to this issue.

Q: What is the cause of the /dev/block/dm-0 read-only issue in Android O?

A: The /dev/block/dm-0 read-only issue in Android O is caused by the secure boot process and read-only file system layout. The system partition is mounted as a read-only file system by default, and any changes made to it require a remount operation.

Q: How do I check the device permissions of /dev/block/dm-0?

A: To check the device permissions of /dev/block/dm-0, use the ls -l command:

ls -l /dev/block/dm-0

This will display the permission string indicating whether the device is read-only or read-write.

Q: How do I remount the system partition in read-write mode?

A: To remount the system partition in read-write mode, use the following command:

mount -o rw,remount /system

If the device is read-only, you will see an error message indicating that the remount operation failed.

Q: What is the secure boot status, and how do I check it?

A: The secure boot status is a flag that indicates whether the system is booted in secure mode or not. To check the secure boot status, use the following command:

getprop ro.boot.secure

If the secure boot status is enabled, you will see a value of 1.

Q: How do I disable secure boot?

A: To disable secure boot, use the following command:

setprop ro.boot.secure 0

This will disable the secure boot process and allow you to remount the system partition in read-write mode.

Q: What are some common issues that can cause the /dev/block/dm-0 read-only issue?

A: Some common issues that can cause the /dev/block/dm-0 read-only issue include:

  • Secure boot enabled: If the secure boot status is enabled, the system partition will be mounted as a read-only file system.
  • Read-only file system: If the system partition is mounted as a read-only file system, any changes made to it will require a remount operation.
  • Device permissions: If the device permissions of /dev/block/dm-0 are set to read-only, the remount operation will fail.

Q: How do I troubleshoot the /dev/block/dm-0 read-only issue?

A: To troubleshoot the /dev/block/dm-0 read-only issue, follow these steps:

  1. Check the device permissions of /dev/block/dm-0 using the ls -l command.
  2. Check the secure boot status using the getprop ro.boot.secure command.
  3. Disable secure boot using the setprop ro.boot.secure 0 command.
  4. Remount the system partition in read-write mode using the mount -o rw,remount /system command.

Conclusion

In conclusion, the /dev/block/dm-0 read-only issue in Android O is a common problem that can be caused by several factors, including secure boot enabled, read-only file system, and device permissions. By following the steps outlined in this article, you should be able to troubleshoot and resolve the issue.

Additional Tips

Here are some additional tips to help you troubleshoot and resolve the issue:

  • Use the adb shell command: If you are using the adb command-line tool, use the adb shell command to access the Android shell and execute the remount command.
  • Check the system logs: Check the system logs to see if there are any error messages indicating the cause of the issue.
  • Use a file system editor: Use a file system editor, such as adb shell or busybox, to edit the system files and make changes to the system partition.

Related Articles

Here are some related articles that may help you troubleshoot and resolve the issue:

  • Android O: Secure Boot and Read-Only File System
  • Android O: Remounting the System Partition
  • Android O: Troubleshooting Common Issues

References

Here are some references that may help you troubleshoot and resolve the issue:

  • Android O: Developer Documentation
  • Android O: System File System Layout
  • Android O: Secure Boot and Read-Only File System