First Mistake As A Sysadmin

# First Mistake As A Sysadmin: Installing Docker Without Understanding Networking Configuration

Welcome to our blog post where we discuss a common mistake made by new sysadmins and DevOps engineers - installing Docker without understanding the networking configuration. This post is designed for experienced system administrators, focusing on practical implementation of self-hosted infrastructure solutions in your homelab or production environment.

Prerequisites

• Ubuntu 20.04 LTS (Focal Fossa) or CentOS 8 Stream (exact versions may vary depending on Docker version)
• Docker CE version 5.0.8 or higher (Download Docker Community Edition)

Solution

Step 1: Install Docker Engine

Install the required package using the following command:

apt-get update && apt-get install -y docker-ce=5.0.8 \
                             docker-ce-cli=5.0.8 \
                             containerd.io

For CentOS, use:

yum install -y docker-ce-19.03.12 docker-ce-clicli

Step 2: Configure Docker Networking

By default, Docker creates a NAT network for your containers. However, if you want to use host networking or custom networks, you’ll need to configure Docker networking properly. Here is an example of how to create a custom bridge network:

cat << EOF | sudo tee /etc/docker/daemon.json
{
  "fixed-cidr": "10.244.0.0/16",
  "iptables": false,
  "log-driver": "journald",
  "log-opts": {
    "max-size": "10m"
  },
  "storage-opt": {"storage-driver": "overlay2"}
}
EOF

Now reload Docker daemon:

sudo systemctl daemon-reload
sudo systemctl restart docker

Step 3: Create and Start a Container

Create a simple Nginx container using the following command:

docker run -d --name mynginx \
          -p 80:80 \
          -v /path/to/mynginx.conf:/etc/nginx/conf.d/default.conf \
          nginx

Step 4: Verify the Setup

Verify that your container is running and exposed on port 80 using the following command:

docker ps

Troubleshooting

If you encounter issues with Docker, check the logs using journalctl -u docker. Also, ensure that your firewall is configured to allow incoming traffic on port 80.

Conclusion

Understanding Docker networking configuration is crucial for a smooth operation of your containers in self-hosted environments. This post provided you with an example setup and step-by-step instructions for creating and configuring custom networks in Docker. Always remember to test your applications thoroughly and keep your infrastructure secure by updating packages regularly, using best security practices, and monitoring your environment.

For more information about Docker, visit the Docker documentation. Happy sysadminning!