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Learn how to diagnose and fix the "Bad magic number in super-block" error when running resize2fs on a logical volume in CentOS 7.
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Troubleshooting Bad Magic Number in Super-block Error on Logical Volume with Resize2fs

When working with logical volumes on CentOS 7, encountering the error message "Bad magic number in super-block while trying to open" can be quite concerning. This error typically occurs when attempting to run the resize2fs command on a logical volume and may prevent further operations on the filesystem. Below, we explore potential causes and solutions for this issue.

Understanding the Error

The message "Bad magic number in super-block while trying to open" indicates that resize2fs cannot recognize the filesystem on the logical volume (LV). This usually means that the expected ext2, ext3, or ext4 filesystem metadata is either absent or corrupted.

Common Causes

Incorrect Filesystem Type: The logical volume you are trying to resize may not have an ext-based filesystem (ext2, ext3, or ext4). The resize2fs tool is specifically designed for these filesystems, so running it on a different type, such as XFS, will trigger this error.

Corrupted Super-block: The super-block contains important metadata about the filesystem. If this section is corrupted, the filesystem appears unrecognizable to resize2fs.

Unformatted Logical Volume: If the logical volume has not been formatted with a filesystem, any operations intended for filesystems will fail, generating errors like this one.

Diagnosing the Problem

Identify Filesystem: Ensure the logical volume contains an ext2, ext3, or ext4 filesystem by running:

[[See Video to Reveal this Text or Code Snippet]]

Replace /dev/your_logical_volume with the path to your specific volume.

Check Super-blocks: Use the dumpe2fs command to check for backup super-blocks and filesystem information:

[[See Video to Reveal this Text or Code Snippet]]

Potential Solutions

Verify Filesystem Type: If you realize the filesystem is not ext-based, consider converting it or using the appropriate resize tool for your filesystem, such as xfs_growfs for XFS filesystems.

Repair Filesystem: If the super-block is corrupted, you can attempt to repair it using e2fsck:

[[See Video to Reveal this Text or Code Snippet]]

You can use one of the alternative super-blocks listed by dumpe2fs.

Format the Logical Volume: If the logical volume is unformatted, you will need to create a filesystem on it:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Encountering the "Bad magic number in super-block" error while running resize2fs can be challenging, but understanding the root causes—incorrect filesystem type, super-block corruption, or an unformatted logical volume—can guide you towards appropriate solutions. Always ensure to back up any important data before proceeding with filesystem repairs or formatting.

By thoroughly diagnosing the issue, you can effectively resolve the error and maintain the integrity of your system's filesystems.