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NABLE TO WRITE TO INTERNAL STORAGE AFTER INSTALLING CRDROID 6.20 ANDROID 10 ON SAMSUNG A520F

Troubleshooting Internal Storage Write Permissions on crDroid 6.20 for Samsung Galaxy A520F

We understand the frustration that arises when a custom ROM installation fails to perform a fundamental function, such as writing to internal storage. After installing crDroid 6.20 (Android 10) on the Samsung Galaxy A520F (Galaxy A5 2017), users frequently encounter issues where file managers, camera applications, and even the system itself cannot write data to the internal storage. This specific problem is a common hurdle in the Android development community, often stemming from partition formatting mismatches, SELinux policies, or encryption conflicts inherent to Samsung’s hardware architecture.

This comprehensive guide is designed to provide a permanent solution to the “unable to write to internal storage” error. We will explore the root causes, diagnose the issue, and provide step-by-step instructions to resolve it using TWRP Recovery, Magisk, and specific kernel configurations. Our methodology ensures that the Samsung Galaxy A520F operates seamlessly with crDroid 6.20, restoring full read/write capabilities to the device.

Understanding the Root Cause of Storage Write Failures

To effectively resolve the storage write issue on the Samsung A520F, we must first understand the technical landscape of Android partitioning and Samsung’s specific implementation. The inability to write to internal storage is rarely a bug within crDroid itself but rather a mismatch between the ROM’s expectations and the existing partition state on the device.

File System Incompatibility: F2FS vs. EXT4

The Samsung Galaxy A520F shipped with Android 7.0 Nougat utilizing the Flash-Friendly File System (F2FS) for its userdata partition. F2FS is optimized for NAND flash storage, offering better performance and longevity compared to the older EXT4 file system. However, many custom ROMs and kernels are compiled with default support for EXT4. When a user flashes a ROM expecting an EXT4 partition on a device formatted with F2FS (or vice versa), the mount process can fail or result in read-only access. While Android 10 generally supports both, kernel-level drivers and fstab (file system table) configurations must align perfectly with the partition format.

Encryption and Metadata Encryption

Samsung devices utilize a specific encryption scheme that differs significantly from AOSP (Android Open Source Project) implementations. The A520F uses File-Based Encryption (FBE). When flashing crDroid 6.20, if the metadata encryption is not properly wiped or formatted, the OS may encounter permission denials when attempting to write to the decrypted userdata partition. This often manifests as a storage error despite the storage appearing to be mounted correctly in TWRP.

SELinux Context Mismatch

Security-Enhanced Linux (SELinux) is a mandatory access control system implemented in Android. Custom ROMs like crDroid enforce strict SELinux policies. If the file system’s context labels (assigned to files and directories) are incorrect—often due to dirty flashing or improper partition formatting—SELinux will deny write operations. This is a security feature designed to prevent malicious apps from modifying system files, but it can incorrectly block legitimate processes if the labels are corrupted.

Vendor Partition and Kernel Discrepancies

The vendor partition contains hardware-specific configurations and libraries. For the Samsung A520F, it is critical that the kernel and vendor blobs are compatible with the specific crDroid build. If the kernel used is derived from a stock Samsung firmware that expects a specific encryption footer or partition layout, it may fail to communicate correctly with the AOSP-based recovery or ROM, leading to storage I/O errors.

Prerequisites for Resolving Storage Issues on Samsung A520F

Before attempting any modifications to resolve the write permission errors, we must ensure the Samsung Galaxy A520F is properly prepared. Proceeding without these prerequisites can result in a hard brick, rendering the device unusable.

  1. Bootloader Unlock: The bootloader must be unlocked to flash custom recoveries and ROMs. This process wipes all data on the device.
  2. TWRP Recovery (or similar): A custom recovery is required to manage partitions and flash necessary ZIP files. Ensure you are using a version specifically built for the Samsung Galaxy A520F (a5y17lte).
  3. USB Drivers: Samsung USB drivers must be installed on your PC to ensure ADB and Fastboot communication.
  4. ADB and Fastboot Tools: Platform-tools must be accessible via your computer’s command line.
  5. Battery Charge: Ensure the device has at least 60% battery to prevent shutdowns during critical flashing operations.

Method 1: Correct Formatting via TWRP Recovery

The most direct way to fix write permission errors is to ensure the userdata partition is formatted correctly for crDroid 6.20. We will perform a clean format of the data partition, which removes encryption remnants and sets the correct file system.

Booting into TWRP Recovery

  1. Power off the Samsung Galaxy A520F completely.
  2. Press and hold Volume Up + Home + Power buttons simultaneously.
  3. Release the buttons when the Samsung logo appears, but keep holding Volume Up until the TWRP interface loads.

Performing a Factory Reset and Format Data

A simple “wipe data” is often insufficient due to encryption. We must explicitly format the data partition.

  1. Navigate to the Wipe menu in TWRP.
  2. Select Format Data (do not confuse this with “Factory Reset,” which only wipes specific folders).
  3. Type yes to confirm the format. This will erase all user data and convert the file system to the standard format compatible with AOSP-based ROMs.
  4. Go back to the main menu and select Advanced Wipe.
  5. Select Cache, Dalvik / ART Cache, and System.
  6. Swipe to wipe these partitions. This ensures no old system files interfere with the new installation.

Flashing crDroid 6.20 and GApps

  1. Transfer the crDroid 6.20 ZIP and the corresponding Google Apps (GApps) package (typically OpenGApps or MindTheGApps for Android 10) to your device’s internal storage or SD card.
  2. Navigate to the Install menu in TWRP.
  3. Select the crDroid 6.20 ZIP file.
  4. Swipe to confirm flash.
  5. Immediately after, select the GApps ZIP and flash it.
  6. Do not reboot yet.

Method 2: Kernel and Modem Configuration

If formatting data does not resolve the write permissions, the issue likely lies with the kernel or the modem (radio) firmware. The Samsung A520F requires specific baseband versions to function correctly with custom ROMs.

Selecting the Correct Kernel

crDroid 6.20 relies on a kernel that supports the AOSP HAL (Hardware Abstraction Layer). Many users opt for custom kernels like ThunderKernel or KrexelKernel which are optimized for the A520F and offer better compatibility with Android 10.

  1. Download a compatible custom kernel (Look for kernels labeled for Android 10 / crDroid / LineageOS).
  2. In TWRP, go to Install and select the Kernel ZIP.
  3. Swipe to flash.
  4. Wipe Cache/Dalvik again after flashing the kernel to prevent conflicts.

Updating Modem (Baseband)

Outdated modem firmware can cause system instability and storage mounting issues. It is highly recommended to flash the latest modem available for the A520F that is known to work with Android 10.

  1. Locate a stable modem (Baseband) image compatible with Android 10 (often extracted from the latest stock Samsung firmware).
  2. Flash the modem image in TWRP via the Install menu (if packaged as a ZIP) or via the Install Image option if it is a .img file.
  3. Reboot to system after flashing.

Method 3: Using Magisk Modules to Fix Permissions

If the issue persists after a clean install, we can utilize Magisk to apply runtime permission fixes and SELinux context corrections. This method is non-intrusive and can be reversed easily.

Installing Magisk via TWRP

  1. Download the latest Magisk ZIP (ensure it is compatible with Android 10).
  2. Boot into TWRP Recovery.
  3. Go to Install and flash the Magisk ZIP.
  4. Reboot to system.

Essential Magisk Modules for Storage Access

Once Magisk is installed and the Magisk Manager app is set up, we can install specific modules available in the Magisk Module Repository (accessible via the Magisk Manager app or our repository at Magisk Modules). These modules help bridge the gap between crDroid and Samsung’s hardware.

  1. Universal SAR (System-As-Root) Module:

    • crDroid 6.20 often utilizes a SAR layout. If the device is not detecting storage correctly due to mount points, a Universal SAR module can remount the partitions correctly.
    • Action: Open Magisk Manager -> Modules -> Search for “Universal SAR” -> Install -> Reboot.

  2. F2FS Support Modules:

    • If the internal storage is formatted as F2FS but the kernel lacks full write support, a specific F2FS optimization module can enable full read/write speeds and permissions.
    • Action: Search for “F2FS” in the Magisk Module Repository. Install only if you suspect the file system is the issue.

  3. Volume Key Selector Module:

    • While not directly fixing storage, this helps in navigating recovery scripts that automate permission fixing (often used in scripts like “Dynamic Partitions Helper”).
    • Action: Install via Magisk Manager.

Manual Permission Fix via Termux (Advanced)

For users comfortable with the command line, we can manually reset SELinux contexts using Termux running as root.

  1. Install Termux from the Play Store or F-Droid.
  2. Install the Termux:Root add-on or use Magisk Manager to install the “Terminal” component.
  3. Open Termux and type:
    su
setenforce 0
  4. This temporarily sets SELinux to Permissive. If storage writing begins to work, the issue is definitively SELinux policy enforcement.
  5. To make this permanent (not recommended for security but for testing):
    • Create a service script in /data/adb/service.d/ that runs setenforce 0 on every boot.
  6. To fix contexts properly without disabling security, execute:
    chcon -R u:object_r:system_file:s0 /system
restorecon -R /data
    Note: Be extremely careful with these commands. Incorrect usage can break the system.

Troubleshooting Specific Error Messages

While applying the fixes above, you may encounter specific error messages. We have outlined the solutions for the most common errors related to the Samsung A520F and crDroid.

“Insufficient Storage Space” Despite Free Space

This error often occurs when the Media Storage database is corrupted or when the /data/media folder (emulated storage) has incorrect permissions.

Solution:

  1. Boot into TWRP.
  2. Open the File Manager tool in TWRP.
  3. Navigate to /data/media/0/.
  4. Look for a file named .nomedia. Delete it.
  5. Navigate to /data/system/ and delete media.db and media.db-journal (if they exist).
  6. Reboot to system. The system will rebuild the media database.

“Error: Mount: Read-only File System”

This indicates that the partition is mounted as read-only, usually due to a file system error or encryption lock.

Solution:

  1. Boot into TWRP.
  2. Go to Mount.
  3. Uncheck Data (this unmounts it).
  4. Select Repair or Change File System.
  5. Choose Ext4 (standard) or F2FS (if you know the partition supports it). We recommend Ext4 for maximum stability with crDroid 6.20.
  6. Swipe to repair/format.
  7. Re-flash crDroid and GApps.

Camera Cannot Save Photos

The camera app failing to save is a direct symptom of storage write failure.

Solution:

  1. Ensure Location permissions are granted to the Camera app (some Android 10 builds require location for saving photos due to scoped storage).
  2. Check if the internal storage is mounted as emulated. Use a root file explorer (like MiXplorer or Root Explorer) to verify that /sdcard is symlinked to /data/media/0.
  3. If not, manually create the symlink via Termux:
    su
ln -s /data/media/0 /sdcard

Advanced Diagnostics: Analyzing Logcats

If the standard fixes fail, we must look at the system logs to identify the exact cause of the I/O failure. This requires a PC with ADB (Android Debug Bridge) installed.

  1. Enable USB Debugging: On the Samsung A520F, go to Settings > About Phone > Tap Build Number 7 times to unlock Developer Options. Then enable USB Debugging.
  2. Connect to PC: Connect the phone to your computer via USB.
  3. Open Command Prompt/Terminal: Navigate to your ADB directory.
  4. Clear Logs: Run adb logcat -c.
  5. Capture Logs: Run adb logcat > storage_log.txt.
  6. Reproduce the Error: Disconnect the phone and try to save a file or take a photo. Reconnect and stop the log capture (Ctrl+C).
  7. Analyze: Open storage_log.txt and search for keywords like:
    • EACCES (Permission denied)
    • EPERM (Operation not permitted)
    • SELinux
    • MountService
    • FUSE

If you see repeated SELinux denials, the issue is policy-based. If you see EPERM during mount operations, the issue is file system or kernel-based.

Preventing Future Storage Issues

To ensure the Samsung Galaxy A520F remains stable with crDroid 6.20, we recommend adhering to the following best practices:

Final Recommendations for the Samsung A520F Community

We have covered the primary methods to resolve the “Unable to write to internal storage” issue on the Samsung Galaxy A520F running crDroid 6.20 (Android 10). The most effective solution is usually a complete format of the data partition via TWRP followed by a clean installation of the ROM and a compatible kernel.

By understanding the interplay between the file system (F2FS vs. EXT4), encryption (FBE), and SELinux policies, users can diagnose and fix these errors systematically. For additional support, specific modules, and tools to enhance your custom Android experience, we invite you to visit our Magisk Module Repository at Magisk Modules. Our resources are curated to assist users in overcoming the complex challenges of Android customization, ensuring that devices like the aging but capable Galaxy A520F continue to run the latest software smoothly.

Should these steps fail, verify that the crDroid 6.20 build specifically supports the a5y17lte variant. Using a ROM intended for a different device model is a common cause of irreparable system errors. Always check the XDA Developers forum or the official crDroid GitHub for the specific device tree status before proceeding.

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