fsck (file system check) — File system integrity check and repair
Linux / File and disk management / fsck.html
A checking tool that verifies file system metadata and repairs errors interactively.
Basic Information
| Command Name | fsck (file system check) |
|---|---|
| One-line Introduction | A checking tool that verifies file system metadata and repairs errors interactively. |
| Provided by | e2fsprogs / util-linux (preinstalled on most distributions) |
| Official Documentation | https://man7.org/linux/man-pages/man8/fsck.8.html |
| Supported Operating Systems | Linux, WSL |
| Installation Status | Installed by default (no separate installation needed) |
| Category | Linux file and disk management (tags: filesystem, check, repair, e2fsck) |
What is this command?
fsck checks the superblock, inodes and block bitmaps of a file system to find damaged metadata. Depending on the file system type it delegates to a tool such as e2fsck or xfs_repair.
It must be run on an unmounted file system; during boot systemd performs the check automatically. The run may continue with interactive prompts asking whether to repair each problem.
What problems does it solve?
- A file system may be damaged after an unclean shutdown
- Mounting fails with metadata corruption messages
- You want to verify integrity before replacing a disk
- The boot-time check keeps repeating
Key features
Read-only check
The -n option reports problems without changing anything.
- When to use: You want a diagnosis before changing anything
- What you get: A summary of found errors and an exit code
- Limitations: The file system stays untouched even if errors remain.
Automatic repair
The -y option answers yes to every question and repairs in bulk.
- When to use: You have a backup and need a fast repair
- What you get: A repaired file system
- Limitations: An incorrect repair can damage data further.
File system specific tools
ext4 uses e2fsck, XFS uses xfs_repair and Btrfs uses btrfs check.
- When to use: You need a check tailored to one file system
- What you get: Results from the appropriate checker
- Limitations: Options and repair policies differ between tools.
Installation and usage
Check whether it is installed
fsck --versionsudo apt install e2fsprogs # Debian/Ubuntu sudo dnf install e2fsprogs # Fedora
Real-world examples
Read-only check
Unmount the file system, then check without changes.
sudo umount /dev/sdb1
sudo fsck -n /dev/sdb1Repair automatically
Repair in bulk when a backup exists.
sudo fsck -y /dev/sdb1ext4 specific check
Use e2fsck and also scan for bad blocks.
sudo e2fsck -f -c /dev/sdb1