🔧 Fixing File System Corruption: Simple Guide

Let’s fix file system corruption on your Alpine Linux system! 🛠️ This guide uses easy steps and simple words. We’ll recover your data and restore your system! 😊

🤔 What is File System Corruption?

File system corruption is like having pages torn out of a book or words scrambled on the pages!

Think of file system corruption like:

• 📝 A damaged library catalog that can’t find books
• 🔧 A broken index that points to wrong information
• 💡 A puzzle with missing or wrong pieces

🎯 What You Need

Before we start, you need:

• ✅ Alpine Linux system (may need live boot USB)
• ✅ Root access or sudo permissions
• ✅ Backup of important data (if possible)
• ✅ Basic knowledge of terminal commands

📋 Step 1: Detect File System Issues

Check for Corruption Signs

First, let’s identify if you have file system corruption! 😊

What we’re doing: Looking for warning signs that indicate your file system might be damaged or corrupted.

# Check system logs for file system errors
dmesg | grep -i "error\|corrupt\|bad\|fail"

# Check kernel ring buffer for I/O errors
dmesg | grep -i "i/o error\|input/output error"

# Look for file system specific errors
journalctl | grep -i "ext4\|xfs\|btrfs"

# Check for recent system crashes
last reboot

# Monitor for ongoing issues
tail -f /var/log/messages | grep -i error

What this does: 📖 Shows you error messages that indicate file system problems.

Common warning signs:

[12345.678901] EXT4-fs error (device sda1): ext4_mb_generate_buddy:1234: group 5, block bitmap and bg descriptor inconsistent
[12345.678902] I/O error, dev sda, sector 123456
[12345.678903] Buffer I/O error on device sda1, logical block 12345
[12345.678904] lost page write due to I/O error on sda1

What this means: These messages indicate file system corruption! ⚠️

💡 Important Tips

Tip: Stop using the corrupted drive immediately to prevent further damage! 💡

Warning: Always backup data before attempting repairs! ⚠️

🛠️ Step 2: Boot from Live System

Use Live USB for Repairs

Now let’s boot from a live system to safely repair corruption! 😊

What we’re doing: Booting from a live USB to unmount and repair the corrupted file system safely.

# If corruption prevents normal boot, create Alpine live USB
# Download Alpine Linux ISO
wget https://dl-cdn.alpinelinux.org/alpine/v3.18/releases/x86_64/alpine-standard-3.18.4-x86_64.iso

# Create bootable USB (replace /dev/sdX with your USB device)
dd if=alpine-standard-3.18.4-x86_64.iso of=/dev/sdX bs=4M status=progress

# Boot from USB and become root
sudo su -

# Install file system tools
apk update
apk add e2fsprogs xfsprogs btrfs-progs dosfstools

# List available disks
lsblk -f
fdisk -l

Expected output:

NAME   FSTYPE LABEL  UUID                                 FSAVAIL FSUSE% MOUNTPOINT
sda                                                                      
├─sda1 ext4   boot   12345678-1234-1234-1234-123456789012               
├─sda2 ext4   root   87654321-4321-4321-4321-210987654321               
└─sda3 swap          abcdef12-3456-7890-abcd-ef1234567890               

What this means: You can now safely access and repair the corrupted drive! 🎉

🎮 Step 3: Check File System Integrity

Run File System Checks

Let’s check the extent of corruption! 🎯

What we’re doing: Using file system check utilities to scan for and identify corruption without making changes yet.

# For ext4 file systems (most common)
fsck.ext4 -n /dev/sda2

# For ext3 file systems
fsck.ext3 -n /dev/sda2

# For XFS file systems
xfs_check /dev/sda2

# For BTRFS file systems
btrfs check /dev/sda2

# Check all file systems automatically
fsck -A -R -y -n

Code explanation:

• -n: Read-only check, no repairs yet
• -y: Automatically answer “yes” to repair prompts
• -A: Check all file systems in /etc/fstab
• -R: Skip root file system when checking all

Example output for corrupted ext4:

e2fsck 1.47.0 (5-Feb-2023)
/dev/sda2: recovering journal
/dev/sda2 contains a file system with errors, check forced.
Pass 1: Checking inodes, blocks, and sizes
Inode 1234567 has imagic flag set. Clear? no

Pass 2: Checking directory structure
Entry 'testfile' in /home/user (1234568) has deleted/unused inode 1234569. Clear? no

Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Inode 1234567 ref count is 2, should be 1. Fix? no

/dev/sda2: ***** FILE SYSTEM WAS MODIFIED *****
/dev/sda2: 123456/654321 files (0.1% non-contiguous), 987654/2468024 blocks

Great job! We found the corruption issues! 🌟

📊 Step 4: Repair File System Corruption

Fix the Corruption

Now let’s repair the file system corruption! 😊

What we’re doing: Running file system repair tools to fix the corruption we identified in the previous step.

# IMPORTANT: Unmount the file system first
umount /dev/sda2

# For ext4 repairs (answer 'y' to all questions)
fsck.ext4 -y /dev/sda2

# For more aggressive ext4 repairs
e2fsck -fyD /dev/sda2

# Alternative: Force check even if clean
fsck.ext4 -f /dev/sda2

# For XFS repairs
xfs_repair /dev/sda2

# For BTRFS repairs
btrfs check --repair /dev/sda2

# Check repair results
fsck.ext4 -n /dev/sda2

Repair process output:

e2fsck 1.47.0 (5-Feb-2023)
/dev/sda2: recovering journal
Pass 1: Checking inodes, blocks, and sizes
Inode 1234567 has imagic flag set. Clear? yes

Pass 2: Checking directory structure
Entry 'testfile' in /home/user (1234568) has deleted/unused inode 1234569. Clear? yes

Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Inode 1234567 ref count is 2, should be 1. Fix? yes

Pass 5: Checking group summary information
Block bitmap differences: -12345 -12346 -12347
Fix? yes

Free blocks count wrong (987650, counted=987653).
Fix? yes

/dev/sda2: ***** FILE SYSTEM WAS MODIFIED *****
/dev/sda2: 123453/654321 files (0.1% non-contiguous), 987651/2468024 blocks

Awesome work! File system corruption has been repaired! 🌟

🎮 Let’s Try It!

Time for hands-on practice! This is the fun part! 🎯

What we’re doing: Testing the repaired file system to make sure everything works correctly.

# Mount the repaired file system
mount /dev/sda2 /mnt

# Check if mount succeeded
mount | grep sda2

# Test basic file operations
ls -la /mnt
touch /mnt/test-file
echo "File system test" > /mnt/test-file
cat /mnt/test-file

# Check file system statistics
df -h /mnt
du -sh /mnt/*

# Verify file system integrity again
fsck.ext4 -n /dev/sda2

# Check for lost+found directory
ls -la /mnt/lost+found/

# Unmount safely
umount /mnt

You should see:

/dev/sda2 on /mnt type ext4 (rw,relatime)

total 24
drwxr-xr-x  3 root root  4096 Jun  3 15:30 .
drwxr-xr-x 19 root root  4096 Jun  3 15:30 ..
drwx------  2 root root 16384 Jun  3 14:20 lost+found
-rw-r--r--  1 root root    16 Jun  3 15:31 test-file

File system test

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2        20G  1.2G   18G   7% /mnt

/dev/sda2: clean, 123453/654321 files, 987651/2468024 blocks

Awesome work! File system is working perfectly! 🌟

📊 Quick Summary Table

🌐 Step 5: Recover Lost Data

Check Lost+Found Directory

Let’s recover any files that were rescued during repair! 🌐

What we’re doing: Examining the lost+found directory where fsck places recovered files that lost their directory entries.

# Mount file system if not already mounted
mount /dev/sda2 /mnt

# Check lost+found directory
ls -la /mnt/lost+found/

# Look for recovered files
find /mnt/lost+found/ -type f -exec file {} \;

# Identify file types
find /mnt/lost+found/ -type f -exec file {} \; | grep -E "(text|ASCII|UTF-8)"

# Try to identify valuable files
find /mnt/lost+found/ -type f -size +1k | head -10

# Example: examine recovered files
for file in /mnt/lost+found/*; do
    if [ -f "$file" ]; then
        echo "=== File: $file ==="
        file "$file"
        head -5 "$file" 2>/dev/null
        echo
    fi
done

What this does: Helps you identify and recover files that were saved during the repair process! 📚

Example: Advanced Recovery Techniques 🟡

What we’re doing: Using specialized tools for more comprehensive data recovery when standard fsck isn’t enough.

# Install additional recovery tools
apk add testdisk photorec ddrescue

# Use testdisk for partition recovery
testdisk /dev/sda

# Use photorec for file recovery
photorec /dev/sda2

# Create disk image for safe recovery
ddrescue /dev/sda2 /mnt/backup/disk-image.img /mnt/backup/recovery.log

# Mount disk image for analysis
losetup /dev/loop0 /mnt/backup/disk-image.img
fsck.ext4 -n /dev/loop0

# Use debugfs for advanced ext4 recovery
debugfs /dev/sda2
# Inside debugfs:
# ls -d /path/to/deleted/files
# logdump
# quit

# Scan for deleted files
extundelete /dev/sda2 --restore-directory /home/user/documents

What this does: Provides advanced recovery options for severely corrupted file systems! 🌟

🚨 Fix Common Problems

Problem 1: Repair fails with “device busy” ❌

What happened: Cannot repair because file system is in use. How to fix it: Boot from live system and unmount!

# Check what's using the file system
lsof /dev/sda2
fuser -mv /dev/sda2

# Force unmount if necessary
umount -f /dev/sda2

# Boot from live USB if root file system
# Then repair from external system
fsck.ext4 -y /dev/sda2

Problem 2: Extensive corruption requiring rebuild ❌

What happened: File system is too damaged to repair. How to fix it: Backup data and recreate file system!

# Try to backup recoverable data first
mkdir -p /mnt/backup
mount -o ro,noload /dev/sda2 /mnt/backup 2>/dev/null

# Copy recoverable files
rsync -av /mnt/backup/ /mnt/external-drive/ --ignore-errors

# Recreate file system (DESTROYS ALL DATA)
mkfs.ext4 /dev/sda2

# Restore from backup
rsync -av /mnt/external-drive/ /mnt/restored/

Problem 3: Bad sectors causing recurring corruption ❌

What happened: Hardware issues cause repeated file system corruption. How to fix it: Check and remap bad sectors!

# Check for bad sectors
badblocks -v /dev/sda2

# Run full surface scan
badblocks -wsv /dev/sda2

# Check SMART status
smartctl -a /dev/sda

# Mark bad blocks during formatting
mkfs.ext4 -c /dev/sda2

# Add bad block list to existing file system
e2fsck -l bad-blocks.txt /dev/sda2

Don’t worry! These problems happen to everyone. You’re doing great! 💪

💡 Simple Tips

1. Regular backups 📅 - Prevent data loss from corruption
2. Monitor disk health 🌱 - Check SMART status regularly
3. Proper shutdowns 🤝 - Avoid power-off during writes
4. Check file systems periodically 💪 - Run fsck monthly

✅ Check Everything Works

Let’s make sure everything is working:

# Final file system check
fsck.ext4 -n /dev/sda2

# Mount and test functionality
mount /dev/sda2 /mnt
ls -la /mnt/

# Test file operations
echo "Final test $(date)" > /mnt/final-test.txt
cat /mnt/final-test.txt

# Check disk space and inodes
df -h /mnt
df -i /mnt

# Verify no errors in dmesg
dmesg | tail -20

# Check file system parameters
tune2fs -l /dev/sda2 | grep -E "(state|errors|Check)"

# Safely unmount
umount /mnt

# You should see this
echo "File system corruption has been fixed! ✅"

Good output:

/dev/sda2: clean, 123456/654321 files, 987654/2468024 blocks

total 32
drwxr-xr-x  3 root root  4096 Jun  3 16:45 .
drwxr-xr-x 19 root root  4096 Jun  3 15:30 ..
drwx------  2 root root 16384 Jun  3 14:20 lost+found
-rw-r--r--  1 root root    45 Jun  3 16:45 final-test.txt

Final test Mon Jun  3 16:45:12 2025

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2        20G  1.3G   18G   7% /mnt

Filesystem state:         clean
Errors behavior:          Continue
Last checked:             Mon Jun  3 16:45:00 2025
Check interval:           15552000 (6 months)

✅ Success! File system is healthy and fully functional.

🏆 What You Learned

Great job! Now you can:

• ✅ Detect and diagnose file system corruption
• ✅ Boot from live systems for safe repairs
• ✅ Use fsck and other tools to fix corruption
• ✅ Recover lost data from lost+found directories
• ✅ Handle advanced recovery scenarios and bad sectors

🎯 What’s Next?

Now you can try:

• 📚 Setting up automated file system monitoring
• 🛠️ Implementing RAID for fault tolerance
• 🤝 Creating disaster recovery procedures
• 🌟 Building comprehensive backup and recovery systems!

Remember: Every expert was once a beginner. You’re doing amazing! 🎉

Keep practicing and you’ll become a file system expert too! 💫