The fsck (stands for File System Consistency Check) is used to check and repair one or more Linux filesystems.
This check will run automatically at boot time when a filesystem inconsistencies detected. Also, can be run manually as needed.
You can use the fsck command to repair corrupted file systems when the system fails to boot, or a partition can’t be mounted, or if it’s become read-only.
In this article, we’ll see how to use the ‘fsck’ or ‘e2fsck’ command in Linux to repair a corrupted file system.
Note:
- Execute the fsck on an unmounted file systems to avoid any data corruption in the file system.
- For larger file systems, fsck may take a long time to run depending on system speed and disk sizes.
When the file system check is complete, fsck returns one of the following exit code:
| Exit 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 request |
| 128 | Shared-library error |
Common Syntax:
fsck [option] [device or partition or mount point]
Corrupting EXT4 File System
We are going to intentionally corrupt the EXT4 file system by executing the below command. It trash’s randomly selected file system metadata blocks.
Make a Note: Please don’t test this on Production server, as this may damage your data badly.
sudo umount /data
Corrupting the ext4 file
sudo dd if=/dev/zero of=/dev/sdb1 bs=10000 skip=0 count=1 1+0 records in 1+0 records out 10000 bytes (10 kB, 9.8 KiB) copied, 0.00394663 s, 2.5 MB/s
When you try to load the file system, you will see the following error message because it was corrupted.
sudo mount /data mount: /data: wrong fs type, bad option, bad superblock on /dev/sdb1, missing codepage or helper program, or other error.
Repair Corrupted EXT4 & EXT3 File System
You can repair a non-root corrupted ext3 or ext4 file system on a running Linux system. fsck works as a wrapper for the fsck.ext3 and fsck.ext4 commands.
Make a note: If you are not able to unmount some of the Non-root volume due to an issue, boot the system into single user mode or rescue mode to repair it.
Step-1: Unmount the device that you want to run fsck.
sudo umount /dev/sdb1
Step-2: Run fsck to repair the file
sudo fsck.ext4 -p /dev/sdb1
-p: Automatically repair any issues that can be safely fixed without user intervention.
If the above option doesn’t resolve the issue, run the fsck command in the below format.
sudo fsck.ext4 -fvy /dev/sdb1
e2fsck 1.45.6 (20-Mar-2020)
ext2fs_open2: Bad magic number in super-block
fsck.ext4: Superblock invalid, trying backup blocks...
Resize inode not valid. Recreate? yes
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
Block bitmap differences: -65536 -65538 -(65541--65542) -(65546--65547) -(65549--65550) -(65555--65557)
.
.
Fix? yes
Free inodes count wrong for group #0 (8181, counted=8165).
Fix? yes
Free inodes count wrong (327669, counted=327653).
Fix? yes
Padding at end of inode bitmap is not set. Fix? yes
/dev/sdb1: ***** FILE SYSTEM WAS MODIFIED *****
27 inodes used (0.01%, out of 327680)
0 non-contiguous files (0.0%)
0 non-contiguous directories (0.0%)
# of inodes with ind/dind/tind blocks: 0/0/0
Extent depth histogram: 19
43294 blocks used (3.30%, out of 1310464)
0 bad blocks
0 large files
16 regular files
2 directories
0 character device files
0 block device files
0 fifos
0 links
0 symbolic links (0 fast symbolic links)
0 sockets
------------
18 files
Step-3: Once the file system is repaired, mount the partition.
sudo mount /dev/sdb1
2) Repairing LVM Volume with fsck
fsck can be run on LVM logical volumes just like filesystems on standard partitions. Follow the below procedure for repairing a LVM partition:
You can also restore/recover the lvm volume instead of repairing it as needed.
Step-1: Make sure the specific LVM volume is in active state to run fsck. To check the status of LVM, run:
sudo lvscan inactive '/dev/myvg/vol01' [1.00 GiB] inherit ACTIVE '/dev/rhel/swap' [2.07 GiB] inherit ACTIVE '/dev/rhel/root' [<26.93 GiB] inherit
If it’s 'inactive', activate it by running the following command.
sudo lvchange -ay /dev/myvg/vol01 -v Activating logical volume myvg/vol01. activation/volume_list configuration setting not defined: Checking only host tags for myvg/vol01. Creating myvg-vol01 Loading table for myvg-vol01 (253:2). Resuming myvg-vol01 (253:2).
Step-2: Unmount the device or filesystem that you want to run fsck.
sudo umount /dev/myvg/vol01
Step-3: Run fsck to repair the file system. You must enter the path of the LVM volume to run fsck and not an actual physical partition.
sudo fsck.ext4 -fvy /dev/myvg/vol01 e2fsck 1.45.6 (20-Mar-2020) /dev/myvg/vol01: clean, 24/65536 files, 14094/262144 blocks
- -f : Force checking even if the file system seems clean.
- -y : Assume an answer of `yes’ to all questions; allows e2fsck to be used non-interactively.
- -v : Verbose mode
Step-4: Once the file system is repaired, mount the partition.
sudo mount /apps
Conclusion
In this tutorial, we’ve shown you how to repair a corrupted EXT4 filesystems on Linux. You can use the same procedure for EXT3 and other filesystems.
Also, shown you how to run e2fsck on the LVM volumes.
source : https://www.2daygeek.com/fsck-repair-corrupted-ext4-file-system-linux/
– by Magesh Maruthamuthu – 2 Comments.