[ZimaOS] Root Partition (1.2GB) 100% Full causing SSL_ERROR_SYSCALL - How to clear OverlayFS space?

Hi everyone, I am facing a critical issue with my ZimaOS NAS. It started when my Overseerr container stopped loading posters and metadata, although the Web UI remained accessible.

After a long debugging session, I isolated the root cause. It is not a Docker or Network issue, but a storage issue on the system partition.

The Problem: The root partition (/) is 100% full. Since ZimaOS has a very small system partition (1.2GB), this seems to be preventing the system from creating temporary files required for SSL handshakes, causing all external HTTPS requests to fail.

Diagnosis & Logs:

  1. Symptoms: Running curl -v https://www.google.com fails instantly with: OpenSSL SSL_connect: SSL_ERROR_SYSCALL However, curl http://www.google.com (HTTP) works perfectly.

  2. Disk Space: The command df -h / shows: /dev/root 1.2G 1.2G 0 100% /

  3. Deep Analysis: We inspected the filesystem using a bind mount to look “under” the active overlays (sudo mount --bind / /tmp/root_debug). We found that /usr is reporting a size of 2.8GB inside the bind mount. This suggests that the writable layer of the OverlayFS is completely saturated.

What I have tried so far:

  • Ran docker system prune (it only freed about 40MB).

  • Cleared logs in /var/log and vacuumed the systemd journal.

  • Tried removing unused firmware in /usr/lib/firmware.

Despite these efforts, df -h / remains stuck at 100%. I suspect there might be “masked” files (e.g., data written to /var or /usr before the external Data disk was mounted) or zombie files that the system is not releasing.

My Question: On ZimaOS (which uses a read-only/overlay filesystem structure), what is the correct procedure to identify and clean the writable upper layer to unblock the root partition without performing a full factory reset?

Thanks in advance for any help!