DevOps Day 36: Deploying a Simple Nginx Container¶

Today's task was a great refresher on the most fundamental operation in Docker: running a container. My objective was to deploy a simple Nginx web server in a container on one of the app servers. This is the "Hello, World!" of containerized deployments and is a core skill for any DevOps practitioner.

I learned the importance of using lightweight images (like nginx:alpine) and how to correctly use the docker run command to launch a container in the background. This document is my first-person guide to that simple but essential process.

The Task¶

My objective was to deploy a container on App Server 3. The specific requirements were: - Create a container named nginx_3. - Use the nginx image with the alpine tag. - Ensure the container is left in a running state.

My Step-by-Step Solution¶

Connect to the Server: I first logged into App Server 3 (ssh banner@stapp03).
Run the Container: I used a single docker run command to create, name, and start the container in the background.
```
sudo docker run -d --name nginx_3 nginx:alpine
```
Verification: The crucial final step was to confirm that the container was running as expected. I used the docker ps command, which lists all running containers.
```
sudo docker ps
```
The output clearly showed my nginx_3 container with a status of "Up," which was the definitive proof that my task was successful.
```
CONTAINER ID   IMAGE          COMMAND                  STATUS         NAMES
[some_id]      nginx:alpine   "/docker-entrypoint.…"   Up a few seconds   nginx_3
```

Key Concepts (The "What & Why")¶

Docker Container: A container is a standard, isolated package that contains an application and all its dependencies. This ensures the application runs the same way regardless of the environment.
Nginx: A high-performance, open-source web server. It's incredibly popular for its speed and efficiency at serving static content.
nginx:alpine Image: This is a specific "flavor" of the official Nginx image. The :alpine tag signifies that it's built on Alpine Linux, an extremely minimalistic Linux distribution. Using Alpine-based images is a major best practice in the Docker world because:
- Size: They are incredibly small (the nginx:alpine image is only a few MB), which means faster downloads and less disk space used.
- Security: They have a minimal "attack surface." Because they include very few extra libraries or tools, there are fewer potential vulnerabilities for an attacker to exploit.
The -d flag (Detached Mode): This was a critical part of the command. The -d flag tells Docker to run the container in the background and print the container ID. Without this, the container would run in the foreground, and my terminal would be attached to the Nginx server's logs. If I closed my terminal, the container would stop. Running in detached mode is essential for any long-running service like a web server.

Commands I Used¶

sudo docker run -d --name nginx_3 nginx:alpine: The main command for this task.
- docker run: The command to create and run a new container.
- -d: Runs the container in detached (background) mode.
- --name nginx_3: Assigns a specific, human-readable name to the container.
- nginx:alpine: The image (and its tag) to use as the blueprint for the container.
sudo docker ps: My verification command. It lists all currently running containers, allowing me to check the NAME and STATUS to confirm the task was completed successfully.