Named volumes for data sharing in Docker - Commands & Configuration

Introduction

Sometimes, you want to save data from a container or share data between containers. Named volumes let you store data outside the container so it stays safe even if the container stops or is removed.

When you want to keep a database's data safe even if the database container is deleted.

When you want two or more containers to access the same files or folders.

When you want to back up or inspect data created by a container easily.

When you want to avoid losing important files after container updates or crashes.

Config File - docker-compose.yml

docker-compose.yml

version: '3.8'
services:
  app:
    image: nginx:1.23
    volumes:
      - shared-data:/usr/share/nginx/html
  backup:
    image: busybox
    command: sleep 3600
    volumes:
      - shared-data:/backup
volumes:
  shared-data:

This file defines two services: app and backup. Both use the same named volume shared-data. The app service uses it to serve files, and the backup service can access the same files for backup. The volumes section declares the named volume shared-data so Docker manages it outside containers.

Commands

This command starts the services defined in the docker-compose.yml file in the background. It creates the named volume and attaches it to both containers so they can share data.

Terminal

docker-compose up -d

Expected Output

Creating network "default" with the default driver

Creating volume "shared-data" with default driver

Creating app ... done

Creating backup ... done

→

-d - Run containers in detached mode (in the background)

This command lists all Docker volumes on your system, showing that the named volume 'shared-data' was created.

Terminal

docker volume ls

Expected Output

DRIVER    VOLUME NAME

local     shared-data

This command lists the files inside the shared volume folder in the 'app' container to verify the volume is mounted and accessible.

Terminal

docker-compose exec app ls /usr/share/nginx/html

Expected Output

index.html

This command stops and removes the containers and network but keeps the named volume so data is not lost.

Terminal

docker-compose down

Expected Output

Stopping app ... done

Stopping backup ... done

Removing app ... done

Removing backup ... done

Removing network default

Key Concept

Named volumes store data outside containers so it persists and can be shared safely between containers.

Common Mistakes

Using bind mounts instead of named volumes for sharing data.

Bind mounts depend on host paths and can cause permission or portability issues.

Use named volumes declared in Docker Compose or Docker CLI for safer, managed data sharing.

Removing containers with 'docker rm -f' without preserving volumes.

This deletes containers but not volumes, which can cause confusion about leftover data.

Use 'docker-compose down' to stop containers but keep volumes, or explicitly remove volumes if needed.

Summary

Named volumes keep data safe outside containers and allow sharing between containers.

Docker Compose can declare and use named volumes easily in the 'volumes' section.

Use 'docker-compose up -d' to start containers with volumes and 'docker-compose down' to stop without losing data.