How to use the command 'xfs_repair' (with examples)

The xfs_repair command is a comprehensive utility used for repairing XFS filesystems. XFS, short for Extent File System, is known for its high performance and scalability, making it an excellent choice for high-performance workloads like databases and streaming media. Over time, filesystems can become corrupt due to unexpected shutdowns, bad sectors on a disk, or software bugs, among other reasons. The xfs_repair tool addresses these issues by inspecting and correcting inconsistencies within the XFS filesystem.

Use case 1: Repair a partition

Code:

sudo xfs_repair path/to/partition

Motivation:

Repairing a partition is often necessary when you encounter system errors or potential data corruption on an XFS filesystem. In situations where the system fails to mount the filesystem due to inconsistencies, running a repair can restore accessibility, thus preventing data loss and ensuring system stability. For example, if an unexpected power outage occurs while data is being written, it might leave the filesystem in a corrupted state. Using the xfs_repair command can resolve such issues.

Explanation:

• sudo: This command runs xfs_repair with superuser privileges. Repairing a filesystem requires administrative rights because it directly interacts with disk partitions, which are critical to the operating system’s operation and security. Without sudo, the command may not have the necessary permissions to execute properly.

• xfs_repair: This is the core command used to check and repair XFS filesystems. When executed, it performs a series of checks and repairs on the filesystem metadata to ensure the integrity and consistency of the filesystem.

• path/to/partition: This specifies the path to the partition that you wish to repair. It must be the path to an unmounted XFS partition, as attempting to repair a mounted filesystem can lead to further corruption. For example, the path might look like /dev/sda1, where /dev/sda1 represents the specific partition on the disk.

Example Output:

Phase 1 - find and verify superblock...
Phase 2 - using internal log
- zero log...
- scan filesystem freespace and inode maps...
Phase 3 - for each AG...
- scan and clear agi unlinked lists...
- process known inodes and perform inode discovery...
- process newly discovered inodes...
Phase 4 - check for duplicate blocks...
- resetting superclass values
Phase 5 - verify metadata...
Logging process completion at (root inode)
done.

The output generally consists of various phases that the repair process goes through, including finding and verifying the superblock, checking free spaces, verifying metadata, and correcting any discrepancies found. Each of these phases ensures different structural and functional components of the filesystem are intact and consistent, which reflects a thorough process of validating and repairing the filesystem.

Conclusion:

The xfs_repair tool is essential for maintaining the integrity of XFS filesystems in the face of corruption and inconsistencies. This article has illustrated how to use the command to repair a partition, emphasizing the importance of running the tool with administrative privileges on unmounted filesystems to ensure successful repairs. By following the outlined steps, users can avert potential data loss and system instability, safeguarding their data and system performance.