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Volumes & Networks

Comprehensive guide to Docker volume management and network configuration for data persistence and container communication.

Volume Management​

Volume Types​

# Named volumes (recommended for production)
docker volume create myvolume
docker run -v myvolume:/data myapp

# Host bind mounts (good for development)
docker run -v /host/path:/container/path myapp
docker run -v $(pwd):/app myapp

# Anonymous volumes (temporary data)
docker run -v /container/path myapp

# Read-only volumes
docker run -v /host/path:/container/path:ro myapp

# Tmpfs mounts (in-memory storage)
docker run --tmpfs /tmp:rw,noexec,nosuid,size=100m myapp

Volume Commands​

# Create volume
docker volume create myvolume

# Create volume with specific driver
docker volume create --driver local myvolume

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

# List volumes
docker volume ls

# Inspect volume
docker volume inspect myvolume

# Remove volume
docker volume rm myvolume

# Remove unused volumes
docker volume prune

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

Volume Drivers​

# Local driver (default)
docker volume create --driver local myvolume

# NFS volume
docker volume create --driver local \
  --opt type=nfs \
  --opt o=addr=10.0.0.1,rw \
  --opt device=:/exports/data \
  nfs-volume

# CIFS/SMB volume
docker volume create --driver local \
  --opt type=cifs \
  --opt o=addr=10.0.0.1,username=user,password=pass \
  --opt device=//10.0.0.1/share \
  cifs-volume

# Block device volume
docker volume create --driver local \
  --opt type=ext4 \
  --opt device=/dev/sdb1 \
  block-volume

Advanced Volume Operations​

# Copy data between volumes
docker run --rm -v source_vol:/from -v dest_vol:/to alpine sh -c "cp -av /from/* /to/"

# Backup volume to tar
docker run --rm -v myvolume:/data -v $(pwd):/backup alpine tar czf /backup/backup.tar.gz -C /data .

# Restore volume from tar
docker run --rm -v myvolume:/data -v $(pwd):/backup alpine tar xzf /backup/backup.tar.gz -C /data

# Inspect volume usage
docker system df -v

# Find containers using a volume
docker ps -a --filter volume=myvolume

Volume Best Practices​

# In Dockerfile
VOLUME ["/data", "/logs"]

# Use specific mount targets
VOLUME /var/lib/mysql
VOLUME /var/log/nginx

# Avoid anonymous volumes in production
# ✗ Bad
VOLUME /data

# ✓ Good - use named volumes
# docker run -v data_volume:/data myapp

Network Management​

Network Types​

# Bridge network (default)
docker network create mynetwork

# Host network (share host networking)
docker run --network host myapp

# None network (no networking)
docker run --network none myapp

# Overlay network (for swarm)
docker network create -d overlay overlay-network

# Macvlan network (VM-like networking)
docker network create -d macvlan \
  --subnet=192.168.1.0/24 \
  --gateway=192.168.1.1 \
  -o parent=eth0 \
  macvlan-network

Network Commands​

# Create network
docker network create mynetwork

# Create network with specific subnet
docker network create --subnet=172.20.0.0/16 mynetwork

# Create network with custom settings
docker network create \
  --driver bridge \
  --subnet=172.30.0.0/24 \
  --ip-range=172.30.0.0/28 \
  --gateway=172.30.0.1 \
  --aux-address="host1=172.30.0.5" \
  mynetwork

# List networks
docker network ls

# Inspect network
docker network inspect mynetwork

# Connect container to network
docker network connect mynetwork container_name

# Connect with specific IP
docker network connect --ip 172.20.0.100 mynetwork container_name

# Disconnect from network
docker network disconnect mynetwork container_name

# Remove network
docker network rm mynetwork

# Remove unused networks
docker network prune

Container Network Configuration​

# Run with specific network
docker run --network mynetwork nginx

# Run with multiple networks
docker run --network net1 nginx
docker network connect net2 container_name

# Set container hostname
docker run --hostname web-server nginx

# Set DNS servers
docker run --dns 8.8.8.8 --dns 8.8.4.4 nginx

# Set DNS search domains
docker run --dns-search example.com nginx

# Add entries to /etc/hosts
docker run --add-host hostname:IP nginx

# Publish ports
docker run -p 8080:80 nginx                    # Host port 8080 -> Container port 80
docker run -p 127.0.0.1:8080:80 nginx         # Bind to localhost only
docker run -p 8080:80/tcp -p 8080:80/udp nginx # Both TCP and UDP

Network Inspection​

# Show container IP address
docker inspect -f '{{.NetworkSettings.IPAddress}}' container_name

# Show all network settings
docker inspect -f '{{json .NetworkSettings}}' container_name | jq

# Show networks a container is connected to
docker inspect -f '{{json .NetworkSettings.Networks}}' container_name

# List containers in a network
docker network inspect mynetwork

# Test connectivity between containers
docker exec container1 ping container2
docker exec container1 nc -zv container2 80

Network Drivers​

Bridge Driver​

# Default bridge network
docker network create --driver bridge mybridge

# Custom bridge with options
docker network create \
  --driver bridge \
  --subnet=172.25.0.0/16 \
  --ip-range=172.25.240.0/20 \
  --gateway=172.25.0.1 \
  --opt com.docker.network.bridge.name=docker1 \
  --opt com.docker.network.bridge.enable_ip_masquerade=true \
  custom-bridge

Overlay Driver (Swarm)​

# Create overlay network
docker network create \
  --driver overlay \
  --subnet=10.10.0.0/16 \
  --gateway=10.10.0.1 \
  overlay-network

# Overlay with encryption
docker network create \
  --driver overlay \
  --opt encrypted=true \
  encrypted-overlay

Macvlan Driver​

# Create macvlan network
docker network create -d macvlan \
  --subnet=192.168.1.0/24 \
  --gateway=192.168.1.1 \
  -o parent=eth0 \
  macvlan-net

# Run container with macvlan
docker run -d --network macvlan-net --ip=192.168.1.100 nginx

Docker Compose Networking​

Basic Network Configuration​

version: '3.8'

services:
  web:
    image: nginx
    networks:
      - frontend

  api:
    image: node:alpine
    networks:
      - frontend
      - backend

  db:
    image: postgres
    networks:
      - backend

networks:
  frontend:
    driver: bridge
  backend:
    driver: bridge
    internal: true # No external access

Advanced Network Configuration​

version: '3.8'

services:
  web:
    image: nginx
    networks:
      frontend:
        ipv4_address: 172.20.0.100
        aliases:
          - webserver
          - nginx-server

networks:
  frontend:
    driver: bridge
    ipam:
      driver: default
      config:
        - subnet: 172.20.0.0/24
          gateway: 172.20.0.1
    driver_opts:
      com.docker.network.bridge.name: 'docker_frontend'
      com.docker.network.bridge.enable_icc: 'true'

External Networks​

version: '3.8'

services:
  web:
    image: nginx
    networks:
      - default
      - external-network

networks:
  external-network:
    external: true
    name: production-network

Volume & Network Security​

Volume Security​

# Read-only volumes
docker run -v /host/data:/data:ro myapp

# Specific mount options
docker run -v /host/data:/data:rw,Z myapp  # SELinux label

# Tmpfs with security options
docker run --tmpfs /tmp:rw,noexec,nosuid,size=100m myapp

# Volume with specific permissions
docker run -v myvolume:/data myapp
docker exec container chown -R user:group /data
docker exec container chmod 750 /data

Network Security​

# Internal network (no external access)
docker network create --internal internal-net

# Disable inter-container communication
docker network create --opt com.docker.network.bridge.enable_icc=false isolated-net

# Network with custom iptables rules
docker network create \
  --opt com.docker.network.bridge.enable_iptables=true \
  secure-net

Troubleshooting​

Volume Issues​

# Check volume mounts
docker inspect -f '{{json .Mounts}}' container_name | jq

# Check volume permissions
docker exec container ls -la /mount/point

# Check disk space
docker exec container df -h

# Find which containers use a volume
docker ps -a --filter volume=myvolume

# Check volume driver status
docker volume inspect myvolume

Network Issues​

# Test DNS resolution
docker exec container nslookup hostname

# Test connectivity
docker exec container ping target_container
docker exec container nc -zv hostname 80

# Check routing table
docker exec container ip route

# Check network interfaces
docker exec container ip addr show

# Inspect network configuration
docker network inspect network_name

# Check iptables rules
sudo iptables -L DOCKER

Common Solutions​

# Reset network to defaults
docker network prune
docker system prune

# Recreate default bridge
sudo service docker restart

# Fix permission issues
docker exec container chown -R user:group /data
docker exec container chmod -R 755 /data

# Clear volume data
docker volume rm volume_name
docker volume create volume_name

Quick Reference​

Volume Commands​

  • docker volume create name - Create named volume
  • docker volume ls - List volumes
  • docker volume inspect name - Inspect volume
  • docker volume rm name - Remove volume
  • docker volume prune - Remove unused volumes

Network Commands​

  • docker network create name - Create network
  • docker network ls - List networks
  • docker network inspect name - Inspect network
  • docker network connect net container - Connect container
  • docker network rm name - Remove network

Best Practices​

  • Use named volumes for persistent data
  • Use bind mounts for development
  • Create custom networks for multi-container apps
  • Use internal networks for backend services
  • Implement proper backup strategies for volumes
  • Monitor volume and network usage regularly
  • Use read-only mounts when possible
  • Secure networks with proper isolation