troubleshoot app files disappearing after container restart

If files inside your app container disappear after a restart, it’s usually because they were written to the container’s writable layer, which is temporary. Containers are meant to be ephemeral unless you use a volume or bind mount.

Most common causes

1. No persistent volume mounted

   • Files created in /app, /data, etc. inside the container vanish when the container is removed/recreated.

2. App writes to the wrong path

   • Your app may be writing to a directory that isn’t mounted to persistent storage.

3. Container is being recreated, not just restarted

   • docker compose up --build, redeploys, or Kubernetes pod reschedules create a new container filesystem.

4. Permissions or startup script overwrites files

   • An entrypoint/init process may recreate or replace files on each start.

5. Volume is mounted over existing files

   • If you mount an empty volume onto /app, it can hide files that were baked into the image.

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How to troubleshoot

1) Confirm where the files are being written

Check inside the container:

docker exec -it <container> sh
pwd
ls -la
mount

If your app stores files in /app/uploads, /data, etc., verify that exact directory.

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2) Check whether a volume is mounted

Run:

docker inspect <container> --format '{{json .Mounts}}' | jq

Look for:

• Type: volume
• Type: bind

If there’s no mount for the path where files are saved, they won’t persist.

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3) Test persistence

Create a file in the suspected path:

docker exec -it <container> sh -c 'echo test > /app/uploads/test.txt'
docker restart <container>
docker exec -it <container> sh -c 'cat /app/uploads/test.txt'

If it’s gone, that path isn’t persistent.

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4) Inspect your Compose or run command

Example with Docker Compose:

services:
  app:
    image: myapp
    volumes:
      - app-data:/app/uploads

volumes:
  app-data:

Or bind mount:

volumes:
  - ./uploads:/app/uploads

If you’re using docker run, make sure you have something like:

docker run -v mydata:/app/uploads myapp

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5) Check app startup behavior

Look at logs and entrypoint scripts:

docker logs <container>

Search for actions like:

• cleaning temp directories
• reinitializing the database
• copying default files over existing ones

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6) If using Kubernetes

Use:

• PersistentVolume / PersistentVolumeClaim
• mount the PVC to the directory where the app writes data

Example:

volumeMounts:
  - name: app-storage
    mountPath: /app/uploads
volumes:
  - name: app-storage
    persistentVolumeClaim:
      claimName: app-pvc

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Quick rule of thumb

• Code → baked into the image
• Generated/uploads/state/data → store in a volume or external storage
• Logs → send to stdout/stderr or persistent log storage

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If you want, I can help you debug your exact setup

Paste one of these:

• your docker run command
• your docker-compose.yml
• your Kubernetes Deployment/StatefulSet YAML
• the path where files disappear

and I’ll pinpoint the issue.