Read-only file system

The error message "Read-only file system" indicates that the operating system has mounted a storage device in read-only mode, preventing any write operations. This commonly occurs on Linux systems but can also appear in containers, servers, cloud VMs, databases, and applications like Java or Docker that rely on the underlying file system. When a file system becomes read-only, the system allows reading data but blocks modifications to protect data integrity.

When does this error occur?

  • Attempting to create, modify, or delete files on a disk mounted as read-only
  • After an unexpected system shutdown or power failure
  • When disk corruption or file system errors are detected
  • Inside Docker containers using read-only volumes or root filesystems
  • When storage devices reach critical error states or hardware issues

Root cause of Read-only file system

At the OS level, the kernel remounts a file system as read-only when it detects inconsistencies, corruption, or I/O errors. This protective behavior prevents further damage and data loss. In some cases, the file system is intentionally mounted as read-only through configuration, container settings, or security policies.

How to fix the error (step-by-step)

Linux / macOS

Check the current mount status to confirm whether the file system is read-only. 

mount | grep ' ro,'

If the file system should be writable, attempt to remount it. 

sudo mount -o remount,rw /

If remounting fails, run a file system check. This usually requires unmounting the disk or booting into recovery mode. 

sudo fsck -f /dev/sdXN

Docker / containers

Verify whether the container or volume is configured as read-only. 

docker inspect <container_id>

Ensure volumes are not mounted with the ro flag and restart the container if needed.

Java / Spring Boot

If the error appears in application logs, verify that the application write path is located on a writable file system and that the underlying OS mount is not read-only.

Verify the fix

After applying the fix, retry the write operation that previously failed. Creating or modifying a test file without errors confirms that the file system is mounted in read-write mode and functioning normally.

Common mistakes to avoid

  • Ignoring disk or kernel logs that indicate hardware or corruption issues
  • Forcing remounts without checking disk health
  • Running fsck on a mounted file system
  • Assuming application permissions are the root cause
  • Overlooking container or volume mount options

Quick tip

Always monitor disk health and system logs to detect file system issues early and avoid unexpected read-only remounts.

FAQ

Q: Can a system automatically switch back to read-write mode?

A: No. Once remounted as read-only due to errors, manual intervention is required.

Q: Does this error always indicate disk corruption?

A: Not always. It can also be caused by intentional configuration or container settings.

Conclusion

The "Read-only file system" error is a protective OS mechanism that must be resolved by addressing mount settings or disk health; check related ROOT errors on ErrorFixHub for deeper storage troubleshooting.

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