docker-storage

# Docker Storage — 存储与数据持久化 Comprehensive guidance for managing persistent data in Docker. ## When to Use **ALWAYS use this skill when the user mentions:** - "docker volume", "数据卷", "数据持久化" - "bind mount", "tmpfs" - "容器数据怎么保存", "数据不丢失" - "数据库容器怎么持久化" - "备份恢复", "存储驱动" ## 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 ```bash # 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 ```bash # 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) ```bash # 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 ```bash 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 ```bash 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) ```bash docker volume create redisdata docker run -d \ --name redis \ -v redisdata:/data \ -p 6379:6379 \ redis:7-alpine redis-server --appendonly yes ``` ## Backup & Restore ```bash # 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 | ```bash docker info | grep "Storage Driver" # Check current ``` ## Workflow — 推荐配置流程 Step 1: **确定存储类型**: 持久化数据 → Volume；开发热加载 → Bind Mount；临时缓存 → tmpfs Step 2: **创建 Volume**: `docker volume create db_data` Step 3: **挂载到容器**: `docker run -v db_data:/var/lib/mysql mysql` Step 4: **验证**: `docker volume inspect db_data` + `docker exec mysql ls /var/lib/mysql` Step 5: **备份**: `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 — 能力边界（适用与不适用场景） | 分类 | 场景 | 说明 | |------|------|------| | ✅ 能做 | 数据持久化配置（Volume/Bind Mount/tmpfs） | 三类存储的创建、挂载、管理 | | ✅ 能做 | 备份与恢复 | `tar` + `--volumes-from` 备份恢复 | | ✅ 能做 | 存储驱动选型 | overlay2/btrfs/zfs 对比 | | ⚠️ 需条件 | NFS/云存储 Volume 驱动 | 需安装对应驱动插件 | | ⚠️ 需条件 | macOS 下 Bind Mount 性能 | 使用 `:cached`/`:delegated` 或命名 Volume | | ❌ 超范围 | K8s PersistentVolume/PVC | 使用 `docker-production` + K8s 文档 | | ❌ 超范围 | 分布式文件系统（Ceph/GlusterFS） | 系统管理员范畴 | | ❌ 超范围 | 数据库性能优化 | DBA 专业领域 | ## 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. ## 📚 官方文档参考 | 文档 | 地址 | |------|------| | Docker 存储 | 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/ | | 存储驱动 | https://docs.docker.com/storage/storagedriver/ | | docker volume 命令 | https://docs.docker.com/reference/cli/docker/volume/ | ## 🧭 Docker Skills Journey > 📍 **You are here: `docker-storage` — 数据持久化** **← Previous**: `docker-run` / `docker-networking` **→ Next**: `docker-compose` / `docker-security` ## FAQ **Q1: 如何快速上手此技能？** A: 参考上方的快速开始章节，按步骤操作即可。 **Q2: 遇到版本不兼容问题怎么办？** A: 检查依赖版本，使用 lock 文件锁定，参考常见陷阱章节。 **Q3: 如何在生产环境使用？** A: 参考最佳实践章节，确保配置正确，做好监控和日志。 **Q4: 性能如何优化？** A: 参考性能优化相关文档，使用缓存、索引等手段。 **Q5: 如何贡献或反馈问题？** A: 在 GitHub 仓库提交 Issue 或 Pull Request。 **Q6: 是否支持中文？** A: 支持中文文档和中文注释，详见国内适配章节。