Docker Volumes and Persistent Data

# Create
docker volume create mydata

# Use in a container
docker run -d --name db \
  -v mydata:/var/lib/postgresql/data \
  postgres:16

# List volumes
docker volume ls

# Inspect
docker volume inspect mydata

docker run -d --name web \
  -v /home/user/website:/usr/share/nginx/html:ro \
  nginx

services:
  db:
    image: postgres:16
    volumes:
      - pgdata:/var/lib/postgresql/data      # Named volume
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql  # Bind mount

volumes:
  pgdata:

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

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

docker run --rm \
  -v source_vol:/from:ro \
  -v dest_vol:/to \
  alpine sh -c "cp -a /from/. /to/"

services:
  writer:
    image: alpine
    command: sh -c "while true; do date >> /data/log.txt; sleep 5; done"
    volumes:
      - shared:/data

  reader:
    image: alpine
    command: tail -f /data/log.txt
    volumes:
      - shared:/data:ro

volumes:
  shared:

docker run -d --name cache \
  --tmpfs /tmp:size=100m \
  redis:7-alpine

# Remove unused volumes
docker volume prune

# Remove a specific volume
docker volume rm mydata

# Nuclear — remove all stopped containers and their volumes
docker system prune --volumes