1.Docker Volumes 📦

Before I explain Docker Volumes, here is the link to the official documentation of Docker Volumes.

In simple terms, volumes are the preferred way to store and keep data that is created or used by Docker containers.

When you run containers with Docker, they can generate or rely on certain data, such as configuration files, databases, or application outputs. Volumes provide a convenient and reliable method to persist this data. By using volumes, it is ensured that the data remains available even if the containers are stopped, restarted, or removed. It acts as a separate storage space specifically for container data, making it easy to manage and share data between containers as needed.

There is a concept called Bind Mounts. Bind mounts are a way to access and share files or directories between the host machine and a Docker container. Unlike volumes, which are managed by Docker and stored within the Docker environment, bind mounts link specific locations on the host file system directly to the container.

2. Why Volumes over Bind Mount? 🔄

Volumes have several advantages over bind mounts:

Volumes are easier to back up or migrate than bind mounts.
You can manage volumes using Docker CLI commands or the Docker API.
Volumes work on both Linux and Windows containers.
Volumes can be more safely shared among multiple containers.
Volume drivers let you store volumes on remote hosts or cloud providers, encrypt the contents of volumes, or add other functionality.
New volumes can have their content pre-populated by a container.
Volumes on Docker Desktop have much higher performance than bind mounts from Mac and Windows hosts.
Unlike a bind mount, you can create and manage volumes outside the scope of any container.

Create a volume:

docker volume create my-vol

List volumes:

docker volume ls

Inspect a volume:

docker volume inspect my-vol

Remove a volume:

docker volume rm my-vol

Attach a Volume to a Container:

docker run -v myvolume:/path/in/container myimage

Detach a Volume from a Container:

To detach a volume from a running container, you need to stop and remove the container. The volume will still exist and can be attached to other containers if needed.

docker container stop imagename
docker container rm imagename

Understanding Docker Networking

Docker networking allows containers to communicate with each other and with external systems. It provides isolation, security, and the ability to scale applications. Docker uses a pluggable architecture for networking, which means you can choose the best networking driver for your needs. There are several built-in networking drivers:

Bridge: The default driver that creates a private network for containers on the host.
Host: Bypasses the Docker network stack and uses the host’s network directly.
Overlay: Creates a network spanning across multiple Docker hosts, useful for Docker Swarm mode.
Macvlan: Assigns a MAC address to a container and connects it directly to the physical network.

Creating and Managing Docker Networks

To create a new network, you can use the docker network create command. For example, to create a bridge network named "my_bridge_network":

docker network create -d bridge my_bridge_network

To list all available networks:

docker network ls

To inspect a specific network:

docker network inspect my_bridge_network

To remove a network:

docker network rm my_bridge_network

Connecting Containers to Networks

By default, a container connects to the default bridge network when it is created. To connect a container to a specific network, use the --network flag:

docker run -d --name my_container --network my_bridge_network my_image

To connect an existing container to a network:

docker network connect my_bridge_network my_container

To disconnect a container from a network:

docker network disconnect my_bridge_network my_container

Exposing Ports and Linking Containers

To expose a container’s port to the host or other containers, use the -p (publish) or --expose flag:

docker run -d --name my_container -p 80:80 my_image

To link two containers, allowing them to communicate without exposing ports, use the --link flag:

docker run -d --name my_container_1 --link my_container_2 my_image

Troubleshooting Docker Networking

To diagnose network-related issues, you can use the following tools:

docker network inspect: View detailed information about a network.
docker logs: View container logs to check for errors.
docker exec: Execute commands inside a running container to test network connectivity.
ping, traceroute, netstat, and tcpdump: Use standard networking tools to diagnose issues.

Docker Volumes & Networking