How to fix Read-Only EXT4 drive

An external ext4 drive mounts as read-only in Linux usually because the kernel detected file system corruption or an improper unmount and switched it to read-only mode to prevent data loss. It can also be caused by hardware failure or root-only root directory permissions. [1, 2, 3, 4]

How to Fix and Troubleshoot

1. Identify the Drive Partition

Find your external drive's device name (e.g., /dev/sdb1 or /dev/sdc1):

Run: lsblk or df -h

2. Unmount and Repair the File System

You must unmount the drive before running a file system check (fsck):

Unmount the drive: sudo umount /dev/sdX1 (replace sdX1 with your actual partition)

Repair errors: sudo e2fsck -f /dev/sdX1

Follow any prompts to fix or clear blocks. [1, 2, 3, 4]

3. Remount as Read-Write

Once the repair finishes cleanly, mount it back normally: [1]

Mount command: sudo mount -o remount,rw /dev/sdX1 or unplug and plug it back in. [1, 2]

4. Fix Ownership Issues (If Not Corrupted)

If fsck finds no errors but you still cannot write, the root folder of the drive likely belongs to the root user: [1]

Mount the drive manually to a folder or navigate to its mount point.

Change ownership to your current user: sudo chown -R $USER:$USER /path/to/mount/point