🐳 Docker Volumes and Docker Networks

This guide explains two important concepts in Docker — Volumes (for data storage) and Networks (for container communication). Both are essential for managing real-world applications where containers need to store data and talk to each other.

💾 What is a Docker Volume

A Docker Volume is a storage mechanism used to persist data generated or used by containers. Normally, data inside a container is deleted when the container is removed, but with volumes, data stays safe even after deletion.

In short:

• Volumes are used to store and share data between containers.
• They are managed by Docker and stored outside the container’s filesystem.

⚙️ Step 1: Create a Docker Volume

You can create a volume manually using:

docker volume create myvolume

This command creates a volume named myvolume that can be used by any container.

🧩 Step 2: Use Volume in a Container

To attach a volume to a container:

docker run -d \
  --name mycontainer \
  -v myvolume:/usr/share/nginx/html \
  nginx

Explanation:

• -v myvolume:/usr/share/nginx/html → mounts the myvolume to the given path inside the container.
• Any data written to /usr/share/nginx/html inside the container will be stored persistently in myvolume.

🧾 Step 3: Check and Inspect Volumes

To see all volumes:

docker volume ls

To inspect details about a specific volume:

docker volume inspect myvolume

🧹 Step 4: Remove Volumes

Remove an unused volume:

docker volume rm myvolume

Remove all unused volumes:

docker volume prune

💡 Tip: Never use container storage for databases or important files — always use volumes for persistence.

🌐 What is a Docker Network

A Docker Network allows containers to communicate with each other securely and efficiently. By default, containers are isolated — Docker networks connect them together.

In short:

• Containers on the same network can talk to each other using container names.
• You can create multiple custom networks for different applications.

⚙️ Step 1: Create a Docker Network

To create a new network:

docker network create mynetwork

This creates a bridge-type network by default, which allows containers to communicate with each other on the same host.

🧩 Step 2: Run Containers on the Same Network

Run two containers and connect them to the same network:

docker run -d --name app1 --network mynetwork nginx
docker run -d --name app2 --network mynetwork httpd

Explanation:

• Both app1 and app2 are now connected to mynetwork.
• They can communicate using container names, e.g., ping app2 from inside app1.

🧾 Step 3: Inspect Network Details

To see available networks:

docker network ls

To see detailed info about a network:

docker network inspect mynetwork

🧹 Step 4: Remove a Network

To remove a specific network:

docker network rm mynetwork

Remove all unused networks:

docker network prune