Software⏱️ 3 min read📅 2026-06-11

How to Fix: What is EXT4-fs error (device md0): ext4_mb_generate_buddy:739: group 10770, 0 clusters in bitmap, 32768?

EXT4-fs error on Ubuntu Server 12.04 with RAID 5 and EXT4, possible causes and solutions.

Quick Answer: Run fsck to repair the file system and check for disk errors.

📋 Table of Contents

  1. 🛑 Root Causes of the Error
  2. 🚀 How to Resolve This Issue
  3. 💡 Conclusion

EXT4-fs error (device md0): ext4_mb_generate_buddy:739: group 10770, 0 clusters in bitmap, 32768? This error message is typically seen on Linux systems that use RAID 5 with EXT4 file system. The error occurs when the ext4 file system's metadata block allocation fails to generate a buddy table for a specific group. This can happen due to various reasons such as disk errors, filesystem corruption, or incorrect configuration.

This error is frustrating because it prevents the system from functioning correctly and may lead to data loss if not addressed promptly. Fortunately, there are steps you can take to troubleshoot and fix this issue.

🛑 Root Causes of the Error

  • The primary cause of this error is a disk or filesystem corruption that affects the metadata block allocation. This can occur due to various reasons such as hardware failure, software issues, or incorrect configuration.
  • Another possible cause is an incorrect RAID configuration or a mismatch between the number of disks and the stripe size.

🚀 How to Resolve This Issue

Resyncing the RAID array

  1. Step 1: Stop the system and disconnect all storage devices from the server. This ensures that no data is being written to the disk during the resync process.
  2. Step 2: Run the command `mdadm --monitor --scan` to check for any pending resyncs on the RAID array. If a resync is detected, proceed with the next step.
  3. Step 3: Run the command `sudo mdadm --zero-spare=0 --rebuild /dev/md0` to rebuild the RAID array from scratch. This will overwrite all data on the disk and should fix the error.

Running fsck to repair the filesystem

  1. Step 1: Run the command `fsck.ext4 -C /dev/md0` to check the ext4 file system for any errors. If the error is due to a corrupted metadata block, this command may be able to repair it.
  2. Step 2: If the fsck command fails, you may need to use the `ext4_check` tool to manually repair the filesystem. Run the command `sudo e2fsck -C /dev/md0` to start the repair process.

💡 Conclusion

In most cases, resyncing the RAID array is the primary fix method for this error. However, if the issue persists after resyncing, running fsck or using the `ext4_check` tool may be necessary to repair the filesystem. It's essential to back up your data before attempting any repairs and to ensure that you have a working backup system in place.

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