fsck Cheatsheet
Quick reference for fsck: check Linux filesystems, run safe repairs, force checks, review exit codes, and handle boot-time recovery
fsck checks Linux filesystems for errors and can repair problems when a partition is unmounted. This cheatsheet covers safe check patterns, repair modes, boot-time checks, exit codes, and related recovery commands.
Basic Usage
Common fsck command forms.
| Command | Description |
|---|---|
fsck /dev/sdb1 | Check a filesystem |
fsck -n /dev/sdb1 | Check only, do not write changes |
fsck -f /dev/sdb1 | Force a check even if the filesystem looks clean |
fsck -t ext4 /dev/sdb1 | Check only filesystems of the given type |
fsck -A | Check filesystems listed in /etc/fstab |
Safe Repair Workflow
Use this sequence before making repairs.
| Command | Description |
|---|---|
lsblk -f | Identify the device, mount point, and filesystem type |
mount | grep /dev/sdb1 | Confirm whether the device is mounted |
sudo umount /dev/sdb1 | Unmount the filesystem before repair |
sudo fsck -n /dev/sdb1 | Run a read-only check first |
sudo fsck -p /dev/sdb1 | Auto-fix safe problems without prompts |
Repair Modes
Choose how interactive the repair should be.
| Option | Description |
|---|---|
-n | Do not make changes, useful for a safe first pass |
-p | Automatically repair safe problems |
-y | Answer yes to all prompts |
-r | Prompt before each repair |
-f | Force checking even if the filesystem appears clean |
Filesystem Selection
Target one filesystem, one type, or all entries in fstab.
| Command | Description |
|---|---|
sudo fsck /dev/nvme0n1p2 | Check one device directly |
sudo fsck -t ext4 /dev/nvme0n1p2 | Check one device as ext4 |
sudo fsck -A | Check all eligible filesystems in /etc/fstab |
sudo fsck -AR | Check all except the root filesystem |
sudo fsck.ext4 /dev/nvme0n1p2 | Run the filesystem-specific checker directly |
Root Filesystem Recovery
fsck cannot repair the mounted root filesystem on a running system.
| Method | Description |
|---|---|
| Recovery mode | Boot into recovery and choose the filesystem check option |
| Live USB | Boot a live system, identify the root partition, then run fsck there |
fsck.mode=force | Kernel parameter to force a check during boot on systemd systems |
fsck.repair=yes | Kernel parameter to approve repairs during boot |
sudo touch /forcefsck | Older non-systemd pattern to force a boot-time check |
tune2fs Scheduling
Control when ext filesystems are checked automatically.
| Command | Description |
|---|---|
sudo tune2fs -l /dev/sdb1 | grep -i 'last checked|mount count' | Show last check time and mount counters |
sudo tune2fs -c 25 /dev/sdb1 | Run a check after every 25 mounts |
sudo tune2fs -c -1 /dev/sdb1 | Disable mount-count-based checks |
sudo tune2fs -i 1m /dev/sdb1 | Run a check at most once per month |
sudo tune2fs -i 0 /dev/sdb1 | Disable time-based checks |
fstab Pass Values
The sixth /etc/fstab column controls boot-time check order.
| Value | Description |
|---|---|
0 | Do not check this filesystem at boot |
1 | Check first, usually the root filesystem |
2 | Check after root, for other local filesystems |
Example: /dev/sda2 /home ext4 defaults 0 2
Exit Codes
Use exit codes to understand what fsck found.
| Code | Description |
|---|---|
0 | No errors |
1 | Filesystem errors corrected |
2 | System should be rebooted |
4 | Filesystem errors left uncorrected |
8 | Operational error |
16 | Usage or syntax error |
32 | Checking canceled by user |
128 | Shared-library error |
Other Filesystems
Some filesystems use tools other than fsck.
| Filesystem | Tool |
|---|---|
| XFS | xfs_repair |
| Btrfs | btrfs check or btrfs scrub |
| NTFS | ntfsfix |
| FAT/VFAT | fsck.vfat |
| Ext2/3/4 | fsck.ext2, fsck.ext3, fsck.ext4 |
Related Guides
Use these articles for the full workflow around filesystem repair.
| Guide | Description |
|---|---|
Fsck Command in Linux (Repair Filesystem) | Full fsck guide with examples |
How to Check Disk Space in Linux Using the df Command | Check mounted filesystems and free space |
How to Mount and Unmount File Systems in Linux | Unmount a filesystem before repair |
Sudo Command in Linux: Run Commands as Root | Run fsck with the required privileges |