☑️Day 26: Exploring Docker Registry and Networking🚀

🔹Table of Contents :

• Introduction

• Beginner-Level Docker Networking Commands

• Hands-On Practice

  • Task 1: Container Communication on the Same Network

  • Task 2: Custom Subnet and Host Communication

• Key Takeaways

✅1. Introduction

• Docker Registry:

  • A centralized place to store and manage Docker images. It's like a repository for all your containerized applications.

  • Public Registry: Docker Hub is a common public registry.

  • Private Registry: Companies often use private registries for internal image storage.

• Docker Networking:

  • Bridge Network: The default network mode. Containers on the same bridge can communicate with each other.

  • Host Network: The container shares the host’s network stack directly.

  • Overlay Network: Designed for multi-host networks, often used in Docker Swarm or Kubernetes clusters.

  • Custom Networks: You can create your own networks with specific subnets, IP ranges, and more.

✅2. Beginner-Level Commands:

• List Available Networks:

    docker network ls
  

• Create a New Network:

    docker network create --subnet 172.10.0.0/24 mynet123
  

• Run a Container in a Custom Network:

    docker container run -itd --net mynet123 --ip 172.10.0.20 --hostname myubuntu ubuntu:latest
  

• Inspect Network Details:

    docker network inspect bridge
  

• Connect an Existing Container to a Network:

    docker network connect mynet123 container_name
  

• Check Container IP Address:

    docker inspect container_name | grep -i ipaddress
  

• Ping Between Containers:

    docker exec -it container_name /bin/bash
    ping <container_ip_address>
  

✅3. Hands-On Tasks:

Task 1: Container Communication on the Same Network

Create 3 containers—2 on the same network and 1 on a separate network. Test connectivity between them using ping.

1. List Existing Networks:

    docker network ls
   

2. Create a New Network (for the 2 containers):

    docker network create mynet123
   

3. Run Two Containers on the Same Network:

    docker container run -itd --net mynet123 --name container1 ubuntu:latest
    docker container run -itd --net mynet123 --name container2 ubuntu:latest
   

4. Run a Third Container on the Default Bridge Network:

    docker container run -itd --name container3 ubuntu:latest
   

5. Check Container IP Addresses:

    docker inspect container1 | grep -i "IPAddress"
    docker inspect container2 | grep -i "IPAddress"
    docker inspect container3 | grep -i "IPAddress"
   

6. Ping from container1 to container2:

   • First, enter the container1 shell:

    docker exec -it container1 /bin/bash

Now, ping container2:

    ping <container2_ip_address>

7. Try Pinging container3 from container1 (this should fail, as they’re on different networks):

    ping <container3_ip_address>
   

Task 2: Create a Custom Subnet & Communicate Between Containers

Create a custom subnet, run a container on it, and verify connectivity with a custom IP address.

1. Create a Custom Subnet:

    docker network create --subnet 172.10.0.0/24 mynet456
   

2. Run a Container with a Custom IP Address:

    docker container run -itd --net mynet456 --ip 172.10.0.20 --hostname myubuntu --name custom-container ubuntu:latest
   

3. Check the /etc/hosts File Inside the Container (to verify hostname):

    docker exec -it custom-container /bin/bash
    cat /etc/hosts
   

4. Ping the Container to Check Connectivity:

   • From your local machine:

       ping 172.10.0.20
     

✅4. Key Takeaways:

• Docker networking provides flexibility in how containers communicate.

• With Docker Registry, images can be shared and reused across environments.

• Custom networks and subnets offer control over how containers interact with one another, making them ideal for complex environments.

🚀Thanks for joining me on Day 26! Let’s keep learning and growing together!

Happy Learning! 😊

#90DaysOfDevOps

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