Storage Management

Docker provides multiple mechanisms for persisting and sharing data between containers, between containers and the host, and across container restarts. This guide covers volumes, bind mounts, tmpfs mounts, and storage best practices.

Storage Types Overview

Docker offers three primary types of storage mounts:

┌──────────────────────────────────────────────────────┐
│                    Container                          │
│                                                      │
│  ┌──────────┐   ┌──────────┐   ┌──────────────┐    │
│  │  Volume   │   │  Bind    │   │    tmpfs      │    │
│  │  Mount    │   │  Mount   │   │    Mount      │    │
│  └────┬─────┘   └────┬─────┘   └──────┬───────┘    │
└───────┼──────────────┼─────────────────┼─────────────┘
        │              │                 │
        ▼              ▼                 ▼
┌──────────────┐ ┌───────────┐   ┌────────────┐
│Docker Area   │ │Host File  │   │  Host RAM  │
│/var/lib/     │ │System     │   │  (memory)  │
│docker/volumes│ │(any path) │   │            │
└──────────────┘ └───────────┘   └────────────┘

Comparison Table

Feature	Volumes	Bind Mounts	tmpfs Mounts
Managed by Docker	✅ Yes	❌ No	❌ No
Location on host	Docker-managed path	Any path	Memory only
Survives container removal	✅ Yes	✅ Yes (on host)	❌ No
Can be shared between containers	✅ Yes	✅ Yes	❌ No
Supports volume drivers	✅ Yes	❌ No	❌ No
Pre-populated with image data	✅ Yes	❌ No	❌ No
Performance	Native	Native	Fastest
Recommended for	Production data	Development	Sensitive temp data

Docker Volumes

Volumes are the preferred mechanism for persisting data generated by and used by Docker containers.

Creating and Managing Volumes

bash

# Create a named volume
docker volume create my-data

# Create a volume with specific driver and options
docker volume create --driver local \
  --opt type=nfs \
  --opt o=addr=192.168.1.100,rw \
  --opt device=:/path/to/share \
  nfs-volume

# List all volumes
docker volume ls

# Inspect a volume
docker volume inspect my-data

# Remove a specific volume
docker volume rm my-data

# Remove all unused volumes
docker volume prune

# Remove all unused volumes (including anonymous)
docker volume prune --all

Using Volumes with Containers

bash

# Mount a named volume
docker run -d \
  --name db \
  -v my-data:/var/lib/postgresql/data \
  postgres:16

# Using the --mount syntax (more explicit)
docker run -d \
  --name db \
  --mount source=my-data,target=/var/lib/postgresql/data \
  postgres:16

# Mount a volume as read-only
docker run -d \
  --name web \
  -v my-config:/etc/nginx/conf.d:ro \
  nginx:latest

# Anonymous volume (Docker generates a random name)
docker run -d \
  -v /var/lib/data \
  my-app:latest

Volume Mount Syntax Comparison

Syntax	Example	Notes
`-v` / `--volume`	`-v my-vol:/app/data`	Shorter, traditional syntax
`--mount`	`--mount source=my-vol,target=/app/data`	More explicit, recommended

`--mount` Options

Option	Description	Example
`type`	Mount type	`volume`, `bind`, `tmpfs`
`source`	Volume name or host path	`my-vol`, `/host/path`
`target`	Container path	`/app/data`
`readonly`	Mount as read-only	`readonly`
`volume-opt`	Volume driver options	`volume-opt=size=10G`

Bind Mounts

Bind mounts map a file or directory on the host machine to a container path. They are ideal for development workflows.

Using Bind Mounts

bash

# Mount current directory into container
docker run -d \
  --name dev \
  -v $(pwd):/app \
  -w /app \
  node:20 npm start

# Using --mount syntax
docker run -d \
  --name dev \
  --mount type=bind,source=$(pwd),target=/app \
  -w /app \
  node:20 npm start

# Read-only bind mount
docker run -d \
  -v $(pwd)/config:/app/config:ro \
  my-app:latest

# Mount a single file
docker run -d \
  -v $(pwd)/custom.conf:/etc/nginx/nginx.conf:ro \
  nginx:latest

Bind Mount Use Cases

bash

# Development: Live code reloading
docker run -d \
  --name dev-server \
  -p 3000:3000 \
  -v $(pwd)/src:/app/src \
  -v $(pwd)/public:/app/public \
  node:20 npm run dev

# Configuration injection
docker run -d \
  -v /host/config/nginx.conf:/etc/nginx/nginx.conf:ro \
  -v /host/config/ssl:/etc/nginx/ssl:ro \
  nginx:latest

# Log collection
docker run -d \
  -v /var/log/app:/app/logs \
  my-app:latest

tmpfs Mounts

tmpfs mounts store data in the host's memory only. The data is never written to the host filesystem and is removed when the container stops.

bash

# Create a tmpfs mount
docker run -d \
  --name secure-app \
  --tmpfs /app/temp \
  my-app:latest

# Using --mount syntax with size limit
docker run -d \
  --name secure-app \
  --mount type=tmpfs,target=/app/temp,tmpfs-size=100m,tmpfs-mode=1770 \
  my-app:latest

# Multiple tmpfs mounts
docker run -d \
  --tmpfs /app/temp:rw,size=64m \
  --tmpfs /app/cache:rw,size=128m \
  my-app:latest

tmpfs Use Cases

Use Case	Description
Secret handling	Store secrets that should never touch disk
Temporary files	Scratch space that doesn't need persistence
Performance	High-speed I/O for temporary data
Security	Sensitive data that must not persist

Volume Backup and Restore

Backup a Volume

bash

# Backup a volume to a tar file
docker run --rm \
  -v my-data:/source:ro \
  -v $(pwd):/backup \
  alpine:3.19 \
  tar czf /backup/my-data-backup.tar.gz -C /source .

# Backup with a timestamp
docker run --rm \
  -v my-data:/source:ro \
  -v $(pwd):/backup \
  alpine:3.19 \
  tar czf /backup/my-data-$(date +%Y%m%d_%H%M%S).tar.gz -C /source .

Restore a Volume

bash

# Create a new volume
docker volume create my-data-restored

# Restore from backup
docker run --rm \
  -v my-data-restored:/target \
  -v $(pwd):/backup:ro \
  alpine:3.19 \
  tar xzf /backup/my-data-backup.tar.gz -C /target

Copy Data Between Volumes

bash

# Copy data from one volume to another
docker run --rm \
  -v source-vol:/source:ro \
  -v dest-vol:/dest \
  alpine:3.19 \
  cp -a /source/. /dest/

Volumes in Docker Compose

yaml

services:
  db:
    image: postgres:16
    volumes:
      # Named volume for persistent data
      - db-data:/var/lib/postgresql/data
      # Bind mount for initialization scripts
      - ./init-scripts:/docker-entrypoint-initdb.d:ro

  app:
    image: my-app:latest
    volumes:
      # Named volume shared with db
      - uploads:/app/uploads
      # Bind mount for development
      - ./src:/app/src
      # tmpfs for temporary files
      - type: tmpfs
        target: /app/temp
        tmpfs:
          size: 100000000  # 100 MB

  backup:
    image: alpine:3.19
    volumes:
      - db-data:/source:ro
      - ./backups:/backup
    command: tar czf /backup/db-backup.tar.gz -C /source .

volumes:
  db-data:
    driver: local
  uploads:
    driver: local
    driver_opts:
      type: none
      o: bind
      device: /data/uploads

Storage Drivers

Docker uses storage drivers to manage the contents of the image layers and the writable container layer.

Available Storage Drivers

Driver	Description	Recommended For
`overlay2`	Modern, performant, default on most Linux	All Linux distributions
`fuse-overlayfs`	Overlay for rootless containers	Rootless Docker
`btrfs`	Uses Btrfs filesystem features	Btrfs filesystems
`zfs`	Uses ZFS filesystem features	ZFS filesystems
`vfs`	No copy-on-write, uses full copies	Testing only

Configure Storage Driver

json

// /etc/docker/daemon.json
{
  "storage-driver": "overlay2",
  "storage-opts": [
    "overlay2.size=20G"
  ]
}

bash

# Check current storage driver
docker info | grep "Storage Driver"

# Restart Docker after changing storage driver
sudo systemctl restart docker

Storage Best Practices

Do's and Don'ts

✅ Do	❌ Don't
Use named volumes for persistent data	Store important data in container's writable layer
Use bind mounts for development	Use bind mounts in production
Use tmpfs for sensitive temporary data	Store secrets on disk
Backup volumes regularly	Assume volumes are backed up automatically
Use read-only mounts when possible	Give write access when not needed
Clean up unused volumes	Let unused volumes accumulate

Monitoring Disk Usage

bash

# View Docker disk usage summary
docker system df

# Detailed disk usage
docker system df -v

# View volume sizes
docker volume ls -q | xargs -I {} sh -c \
  'echo "{}:" && docker run --rm -v {}:/vol alpine du -sh /vol'

# Clean up all unused Docker data
docker system prune --volumes

Next Steps

Docker Networking Guide — Learn about container networking
Security Best Practices — Secure your storage and data
Docker Compose Quick Start — Use volumes with Compose
Configuration Management — Configure Docker storage drivers
Container Orchestration — Storage in orchestrated environments

Storage Management ​

Storage Types Overview ​

Comparison Table ​

Docker Volumes ​

Creating and Managing Volumes ​

Using Volumes with Containers ​

Volume Mount Syntax Comparison ​

--mount Options ​

Bind Mounts ​

Using Bind Mounts ​

Bind Mount Use Cases ​

tmpfs Mounts ​

tmpfs Use Cases ​

Volume Backup and Restore ​

Backup a Volume ​

Restore a Volume ​

Copy Data Between Volumes ​

Volumes in Docker Compose ​

Storage Drivers ​

Available Storage Drivers ​

Configure Storage Driver ​

Storage Best Practices ​

Do's and Don'ts ​

Monitoring Disk Usage ​

Next Steps ​

Storage Management

Storage Types Overview

Comparison Table

Docker Volumes

Creating and Managing Volumes

Using Volumes with Containers

Volume Mount Syntax Comparison

`--mount` Options

Bind Mounts

Using Bind Mounts

Bind Mount Use Cases

tmpfs Mounts

tmpfs Use Cases

Volume Backup and Restore

Backup a Volume

Restore a Volume

Copy Data Between Volumes

Volumes in Docker Compose

Storage Drivers

Available Storage Drivers

Configure Storage Driver

Storage Best Practices

Do's and Don'ts

Monitoring Disk Usage

Next Steps