Docker containers isolate workloads from the host, but sometimes you want to keep data on an external disk. In this quick tip, you’ll learn how to:

1. Identify your external drive
2. Create a Docker volume that points directly at the block device
3. Bind‑mount it into a container at runtime
4. Define it as a named volume in Docker Compose

1. Identify your external drive

Use lsblk or blkid to find the device path and UUID of your drive:

lsblk -f
# or
blkid

Look for your external disk (for example /dev/sdb1). And note its UUID (be874c01-de77-4084-847e-c874bf1b71e8 in this example).

2. Create a Docker volume from the block device

Create a Docker volume that binds directly to the device:

docker volume create hdd \
  --driver local \
  --opt type=ext4 \
  --opt device=/dev/disk/by-uuid/be874c01-de77-4084-847e-c874bf1b71e8 \
  --opt o=bind

• hdd is the name of your volume.
• type=ext4 should match your filesystem (e.g. ntfs or xfs).
• device points at the block device or its UUID symlink.
• o=bind tells Docker to mount it read/write.

Verify it:

docker volume inspect hdd

3. Bind‑mount at runtime

Use the volume with -v when running a container:

docker run -d \
  --name app \
  -v hdd:/app/data \
  image:latest

This mounts the external drive’s filesystem at /app/data inside the container.

4. Define in Docker Compose

For repeatable setups, add the volume to your docker-compose.yml:

services:
  app:
    image: image:latest
    volumes:
      - hdd:/app/data

volumes:
  hdd:
    external:true

# Or define it directly (skip step 2)
volumes:
  hdd:
    driver: local
    driver_opts:
      type: ext4
      device: /dev/disk/by-uuid/be874c01-de77-4084-847e-c874bf1b71e8
      o: bind

Start it with:

docker-compose up -d

With these steps, Docker will treat your external drive as a normal volume, and data sits right on the disk.