Setting Up a Host-Like Environment Using Docker Containers

This documentation provides a step-by-step guide to create a Docker container that mimics a traditional host environment. The container will be capable of running multiple processes and services using supervisord as the process manager.

Features
Nginx: Web server.
MySQL: Database server.
Supervisord: Process manager to manage multiple services.

Host-Like Environment Setup

1. Create Dockerfile Create a Dockerfile with the following content:

# Use an official Ubuntu base image
FROM ubuntu:latest

# Set environment variables to avoid user prompts during package installations
ENV DEBIAN_FRONTEND=noninteractive

# Update the package list and install necessary packages
RUN apt-get update && apt-get install -y \
    nginx \
    mysql-server \
    supervisor \
    && rm -rf /var/lib/apt/lists/*

# Add supervisor configuration file
COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf

# Expose ports for services (e.g., 80 for nginx, 3306 for MySQL)
EXPOSE 80 3306

# Start supervisord to run multiple services
CMD ["/usr/bin/supervisord"]

Explanation:

Base Image: ubuntu:latest provides a minimal Ubuntu environment.
Environment Variables: DEBIAN_FRONTEND=noninteractive ensures package installations don't prompt for user input.
Package Installation: Installs nginx, mysql-server, and supervisor, followed by cleanup to reduce image size.
Configuration: Copies a custom supervisord configuration file into the container.
**Ports: **Exposes necessary ports for Nginx and MySQL.
Entrypoint: Uses supervisord to manage services within the container.

1. Create supervisord Configuration Create a supervisord.conf file with the following content:

[supervisord]
nodaemon=true

[program:nginx]
command=/usr/sbin/nginx -g "daemon off;"
autorestart=true

[program:mysql]
command=/usr/sbin/mysqld
autorestart=true

Explanation:

supervisord: Runs in the foreground (nodaemon=true).
Nginx: Configured to run in the foreground (daemon off;) and restart automatically if it fails.
MySQL: Configured to restart automatically if it fails.

1. Build the Docker Image Build the Docker image using the Dockerfile and supervisord configuration:

docker build -t my_host_like_env .

1. Run the Docker Container Run the Docker container based on the image you just built:

docker run -d --name my_container -p 80:80 -p 3306:3306 my_host_like_env

Check the container is running using:

docker ps
The output will look something similar like this:

The ps -ef command is commonly used for system monitoring and troubleshooting to check which processes are running, their resource usage, and the commands used to start them.

Exit the container using exit command.

1. Access Services Accessing Nginx Web Server Access Nginx via curl or wget:

curl http://localhost:80

If Nginx is running correctly, this command will fetch the default Nginx welcome page.

Access Nginx logs:

docker exec -it my_container tail -f /var/log/nginx/access.log

This command will show the Nginx access log. You can replace access.log with error.log for error logs.

Accessing MySQL Database Server
Access MySQL via MySQL Client:

Connect to MySQL server running inside the container

docker exec -it my_container mysql -uroot -p

If prompted for a password, the default password is empty (just press Enter). Once connected, you can interact with MySQL as you would on a standard MySQL server.

Access MySQL logs:

docker exec -it my_container tail -f /var/log/mysql/error.log

This command will show the MySQL error log. Replace error.log with query.log for the query log, if configured.

Usage
Managing Services
Inside the running container, you can manage services using supervisorctl:

# Check status of services
supervisorctl status

# Stop a service
supervisorctl stop nginx

# Start a service
supervisorctl start nginx

# Restart a service
supervisorctl restart nginx

Conclusion
You now have a Docker container that simulates a traditional host environment capable of running multiple processes and services. You can extend this setup by adding more services or customizing configurations as per your requirements.