fsck

fsck (file system check) is a command-line utility in Unix-like operating systems used to check and repair filesystems. It verifies the integrity of filesystems, detects and fixes errors, and ensures that the filesystem structure is consistent.

Key Features

• Filesystem Integrity Checking: Scans filesystems for inconsistencies and errors.

• Repair Capabilities: Attempts to automatically repair detected issues.

• Support for Various Filesystems: Works with different filesystem types using specific front-end commands.

Basic Usage

The general syntax for fsck is:

fsck [options] <device>

• [options]: Command-line options for configuring the behavior of fsck.

• <device>: The disk partition or device to check (e.g., /dev/sdX1).

Common Filesystem Types and Their Commands

1. ext2/ext3/ext4

For ext2, ext3, and ext4 filesystems, fsck can be used with the specific filesystem type option:

fsck.ext4 /dev/sdX1

Options:

• -n: No changes; just show what would be done.

• -y: Automatically answer "yes" to all questions.

• -f: Force a check, even if the filesystem seems clean.

2. xfs

For xfs, use the xfs_repair utility instead of fsck:

xfs_repair /dev/sdX1

Options:

• -n: No modifications; just show what would be done.

• -L: Log file damage repair.

3. btrfs

For btrfs, use the btrfs check command:

btrfs check /dev/sdX1

Options:

• --repair: Attempt to repair the filesystem.

• --readonly: Perform a read-only check.

4. vfat

For vfat (FAT32) filesystems, use fsck.vfat:

fsck.vfat /dev/sdX1

Options:

• -a: Automatically fix errors.

• -n: No changes; just show what would be done.

Examples

Check an ext4 Filesystem

To check the filesystem on /dev/sda1:

fsck.ext4 /dev/sda1

Force Check and Repair

To force a check and automatically repair errors:

fsck -f -y /dev/sda1

Check an XFS Filesystem

For XFS, use xfs_repair:

xfs_repair /dev/sda1

Important Considerations

• Unmount Filesystem: It is generally recommended to unmount the filesystem before running fsck to avoid data corruption. If the filesystem cannot be unmounted (e.g., it is the root filesystem), you may need to boot from a live CD or enter recovery mode.

• Data Backup: Always back up important data before performing filesystem checks and repairs, as repairs can potentially lead to data loss.

• Filesystem Type: Ensure you are using the correct fsck variant for your filesystem type. Different filesystems have different tools and options.

Summary

fsck is a powerful utility for maintaining filesystem integrity by checking and repairing file systems. It supports various filesystem types through specific front-end commands and offers options for customizing checks and repairs. Proper use of fsck helps ensure that filesystems remain consistent and reliable, preventing data loss and system issues.