When dealing with EXT3 filesystems, the "Read-only file system" error during file deletion typically indicates one of these scenarios:

1. Filesystem errors forcing remount as read-only
2. Physical write protection (like USB lock switches)
3. Permission issues masked as read-only errors
4. Mount options overriding device capabilities

Before attempting fixes, always verify the actual mount status:

# Check /proc/mounts for real status
cat /proc/mounts | grep sdb1

# Verify block device state
hdparm -r /dev/sdb1

# Check filesystem errors
dmesg | grep EXT3

Method 1: Forced Remount

When the filesystem is clean but erroneously mounted read-only:

mount -o remount,rw /dev/sdb1 /media/usbdisk
# If that fails with "write-protected" error:
mount -o remount,rw,force /dev/sdb1

Method 2: Filesystem Repair

For filesystem errors triggering protective read-only mode:

umount /dev/sdb1
fsck.ext3 -p /dev/sdb1
mount -w /dev/sdb1 /media/usbdisk

When standard fixes fail, consider these approaches:

# Check for hardware write protection
hdparm -r0 /dev/sdb1

# Alternative deletion method using debugfs
debugfs -w /dev/sdb1
debugfs: rm /path/to/file
debugfs: quit

• Always properly unmount USB drives
• Regularly check filesystem integrity
• Consider using EXT4 for better error recovery
• Implement proper backup solutions

When attempting to delete files on a Linux system, you might encounter the frustrating "Read-only file system" error even when your mount command shows the filesystem as mounted with read-write (rw) permissions. This discrepancy between reported and actual permissions often indicates deeper filesystem issues.

The first step is to verify the actual mount status beyond what mount shows:

cat /proc/mounts | grep sdb1
# Sample output showing the real status:
# /dev/sdb1 /media/usbdisk ext3 ro,relatime,data=ordered 0 0

The issue typically occurs when:

• The filesystem encountered errors and remounted itself as read-only
• Physical media problems exist (bad sectors on HDD, failing flash cells on SSD/USB)
• The filesystem wasn't properly unmounted previously
• Hardware write-protection is enabled

Try remounting the filesystem with write permissions:

mount -o remount,rw /media/usbdisk
# For specific device:
mount -o remount,rw /dev/sdb1

If you receive errors about write protection:

hdparm -r0 /dev/sdb1  # Disable read-only flag for disks

When remounting fails, filesystem repair is necessary:

umount /dev/sdb1
fsck -y /dev/sdb1
mount /dev/sdb1 /media/usbdisk

If the filesystem remains read-only but you need to delete files:

# Method 1: Use dd to zero out files
dd if=/dev/zero of=/media/usbdisk/problem-file bs=1M count=1

# Method 2: Change permissions first (if possible)
chattr -i /media/usbdisk/problem-file
rm -f /media/usbdisk/problem-file

To avoid this issue:

• Always properly unmount devices (umount or eject)
• Regularly check filesystem health (smartctl for HDDs)
• Consider using more robust filesystems like ext4 or btrfs
• Implement proper backup strategies

For physically write-protected media (like SD cards with lock switches):

# Check if hardware write protection is enabled
hdparm -r /dev/sdb1
# Output should show "readonly = 0" for writable