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docker-storage

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Updated 10-15 21:48

About this skill

Docker Storage — Storage and Data Persistence

Comprehensive guidance for managing persistent data in Docker.

When to Use

ALWAYS use this skill when the user mentions:

  • "docker volume", "data volume", "data persistence"
  • "bind mount", "tmpfs"
  • "how to save container data", "data not lost"
  • "how to persist database containers"
  • "backup and restore", "storage driver"

Storage Type Comparison

Type Persistence Performance Use Case
Volume ✅ (managed by Docker) High (native) Production databases, shared data
Bind Mount ✅ (host filesystem) High Development (live code sync), config files
Tmpfs ❌ (memory only) Highest Secrets, temp files, sensitive data

Visual Comparison

Volume:                       Bind Mount:               Tmpfs:
  Container                     Container                 Container
     │                              │                        │
  Docker-managed               /host/path                 Memory only
  /var/lib/docker/volumes/        ↕                     (no disk)
     ↕                         Container sees:              ↕
  Container sees:              /container/path           Container sees:
  /data                         = host files              /tmp (in RAM)

Volume Management

# Create & inspect
docker volume create mydata
docker volume ls
docker volume inspect mydata

# Use in container
docker run -v mydata:/var/lib/mysql mysql:8
docker run --mount source=mydata,target=/var/lib/mysql mysql:8  # explicit syntax (recommended)

# Cleanup
docker volume prune      # Remove unused volumes
docker volume rm mydata  # Remove specific volume

Named vs Anonymous Volumes

-v mydata:/data      → Named volume  (mydata) — survives container removal ✅
-v /data             → Anonymous volume — hard to identify later ❌

Bind Mount

# Read-write bind mount
docker run -v $(pwd)/app:/app nginx

# Read-only (protect host files)
docker run -v $(pwd)/config:/etc/nginx:ro nginx

# Explicit syntax
docker run --mount type=bind,source=$(pwd)/app,target=/app nginx

Tmpfs (Memory)

# Ephemeral data, never touches disk
docker run --tmpfs /tmp:rw,noexec,nosuid,size=64m nginx
docker run --mount type=tmpfs,destination=/tmp,tmpfs-size=64m nginx

Database Persistence Patterns

PostgreSQL

docker volume create pgdata
docker run -d \
  --name postgres \
  -e POSTGRES_PASSWORD=secret \
  -v pgdata:/var/lib/postgresql/data \
  -p 5432:5432 \
  postgres:16-alpine

MySQL

docker volume create mysqldata
docker run -d \
  --name mysql \
  -e MYSQL_ROOT_PASSWORD=secret \
  -v mysqldata:/var/lib/mysql \
  -v $(pwd)/my.cnf:/etc/mysql/conf.d/my.cnf:ro \
  -p 3306:3306 \
  mysql:8.4

Redis (Persistence)

docker volume create redisdata
docker run -d \
  --name redis \
  -v redisdata:/data \
  -p 6379:6379 \
  redis:7-alpine redis-server --appendonly yes

Backup & Restore

# Backup (using a temporary container)
docker run --rm \
  -v mysqldata:/source \
  -v $(pwd):/backup \
  alpine tar czf /backup/mysqldata-backup.tar.gz -C /source .

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

Storage Drivers

Driver Status Notes
overlay2 ✅ Default Best for most use cases; copy-on-write
devicemapper Deprecated -
aufs Deprecated -
btrfs/zfs Niche Use if filesystem matches 
docker info | grep "Storage Driver"  # Check current

Workflow — Recommended Configuration Process

Step 1: Determine storage type: persistent data → Volume; development hot reload → Bind Mount; temporary cache → tmpfs Step 2: Create Volume: docker volume create db_data Step 3: Mount to container: docker run -v db_data:/var/lib/mysql mysql Step 4: Verify: docker volume inspect db_data + docker exec mysql ls /var/lib/mysql Step 5: Backup: docker run --rm -v db_data:/source -v $(pwd):/backup alpine tar czf /backup/db.tar.gz -C /source .

Gotchas — Common Pitfalls

  • Anonymous volumes accumulate: Every -v /data (no name) creates a new anonymous volume. → Recovery: docker volume prune cleans all unused; use named volumes: -v mydata:/data.
  • Bind mount paths: Must be absolute. → Recovery: -v $(pwd)/app:/app for docker run; -v ./app:/app works in Compose only.
  • Permission issues with bind mounts: Container UID != host UID → permission denied. → Recovery: --user $(id -u):$(id -g) or RUN chown 1000:1000 /data in Dockerfile entrypoint.
  • Data loss on container removal: Without -v, data is lost when container is removed. --rm flag even worse. → Recovery: Always use named volumes: docker run -v db_data:/var/lib/mysql.
  • macOS bind mount performance: Bind mounts on Docker Desktop Mac are slow. → Recovery: Use :cached or :delegated mount options, or named volumes for better I/O.

Boundary — Capability Boundaries (Applicable and Non-Applicable Scenarios)

Category Scenario Description
✅ Can do Data persistence configuration (Volume/Bind Mount/tmpfs) Creation, mounting, and management of the three storage types
✅ Can do Backup and restore tar + --volumes-from Backup and restore
✅ Can do Storage driver selection overlay2/btrfs/zfs comparison
⚠️ Conditional NFS/cloud storage Volume drivers Requires installation of the corresponding driver plugin
⚠️ Conditional Bind Mount performance on macOS Use :cached/:delegated or named Volume
❌ Out of scope K8s PersistentVolume/PVC Use docker-production + K8s documentation
❌ Out of scope Distributed file systems (Ceph/GlusterFS) System administrator domain
❌ Out of scope Database performance optimization DBA professional domain

When NOT to Use This Skill

❌ Skip ✅ Use Instead
Running containers (no data concerns) docker-run
Multi-container orchestration docker-compose
Kubernetes Storage (PV/PVC) K8s documentation
Docker basics docker-basics

Security & Stability

  • Use :ro for config files that containers should not modify.
  • Never bind mount Docker socket (/var/run/docker.sock) without understanding the security implications.
  • Backup volumes regularly, especially database volumes.
  • No executable scripts bundled. Guidance only.

📚 Official Documentation References

Documentation Address
Docker Storage https://docs.docker.com/storage/
Volumes https://docs.docker.com/storage/volumes/
Bind Mounts https://docs.docker.com/storage/bind-mounts/
tmpfs https://docs.docker.com/storage/tmpfs/
Storage Drivers https://docs.docker.com/storage/storagedriver/
docker volume command https://docs.docker.com/reference/cli/docker/volume/

🧭 Docker Skills Journey

📍 You are here: docker-storage — Data Persistence

← Previous: docker-run / docker-networking → Next: docker-compose / docker-security

FAQ

Q1: How do I quickly get started with this skill? A: Refer to the Quick Start section above and follow the steps.

Q2: What should I do if I encounter version incompatibility issues? A: Check dependency versions, use a lock file to pin them, and refer to the Common Pitfalls section.

Q3: How do I use it in a production environment? A: Refer to the Best Practices section, ensure the configuration is correct, and set up monitoring and logging.

Q4: How can performance be optimized? A: Refer to the performance optimization documentation and use techniques such as caching and indexing.

Q5: How can I contribute or provide feedback? A: Submit an Issue or Pull Request in the GitHub repository.

Q6: Is Chinese supported? A: Chinese documentation and Chinese comments are supported; see the Domestic Adaptation section for details.