fsck Cheatsheet
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 |
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