Docker Volumes

Docker Volumes

Volumes are the preferred way to persist data in Docker.

Volume Types

Creating Volumes

# Create volume
docker volume create my-data

# Create with options
docker volume create \
  --driver local \
  --opt type=nfs \
  --opt o=addr=192.168.1.1,rw \
  --opt device=:/path/to/share \
  nfs-data

Using Volumes

# Mount volume to container
docker run -d \
  -v my-data:/app/data \
  myapp

# Named volume (long form)
docker run -d \
  --mount source=my-data,target=/app/data \
  myapp

# Read-only volume
docker run -d \
  -v my-data:/app/data:ro \
  myapp

Volume Management

# List volumes
docker volume ls

# Inspect volume
docker volume inspect my-data

# Remove volume
docker volume rm my-data

# Remove unused volumes
docker volume prune

# Remove all volumes (dangerous!)
docker volume prune -a

Volume Backup and Restore

# Backup volume
docker run --rm \
  -v my-data:/source:ro \
  -v $(pwd):/backup \
  alpine tar czf /backup/my-data-backup.tar.gz -C /source .

# Restore volume
docker run --rm \
  -v my-data:/target \
  -v $(pwd):/backup:ro \
  alpine tar xzf /backup/my-data-backup.tar.gz -C /target

Database Volume Example

# PostgreSQL with volume
docker run -d \
  --name postgres \
  -v postgres-data:/var/lib/postgresql/data \
  -e POSTGRES_PASSWORD=secret \
  postgres:16

# MySQL with volume
docker run -d \
  --name mysql \
  -v mysql-data:/var/lib/mysql \
  -e MYSQL_ROOT_PASSWORD=secret \
  mysql:8

# MongoDB with volume
docker run -d \
  --name mongo \
  -v mongo-data:/data/db \
  mongo:7

Volume Inspection

# Find volume location
docker volume inspect my-data --format '{{.Mountpoint}}'
# /var/lib/docker/volumes/my-data/_data

# View volume contents (requires root)
sudo ls /var/lib/docker/volumes/my-data/_data

# Or use a container
docker run --rm -v my-data:/data alpine ls -la /data

Volume Driver Options

# Local driver with options
docker volume create \
  --driver local \
  --opt type=btrfs \
  --opt device=/dev/sdb1 \
  btrfs-vol

# NFS volume
docker volume create \
  --driver local \
  --opt type=nfs \
  --opt o=addr=192.168.1.1,rw,nfsvers=4 \
  --opt device=:/share/data \
  nfs-vol

Best Practices

1. Use named volumes for data that should persist
2. Backup regularly especially databases
3. Use read-only when possible (:ro)
4. Prune unused volumes regularly
5. Document volumes in compose files