Creating Custom Docker Images

This guide covers creating custom Docker images specifically designed to work with FeatherPanel's spell system. These images must follow specific requirements to ensure compatibility and security.

Prerequisites

Before creating a Docker image, ensure you have:

Docker installed and running
Basic Docker knowledge (Dockerfile, build process)
Understanding of the target application you're containerizing
Access to a Docker registry for image distribution

Docker Image Requirements

Mandatory Requirements

All FeatherPanel Docker images must follow these requirements:

1. Container User

# Must create a user named 'container'
RUN adduser --disabled-password --home /home/container container

# Must set user and home directory
USER container
ENV USER=container HOME=/home/container

2. Working Directory

# Must set working directory to /home/container
WORKDIR /home/container

3. Entrypoint Script

# Must copy and use entrypoint script
COPY ./entrypoint.sh /entrypoint.sh
CMD ["/bin/bash", "/entrypoint.sh"]

Creating the Dockerfile

Basic Dockerfile Structure

# ----------------------------------
# FeatherPanel Custom Dockerfile
# Environment: [Your Environment]
# Minimum Panel Version: 2.0.0
# ----------------------------------
FROM [base-image]

MAINTAINER [Your Name], <[email protected]>

# Install dependencies
RUN [install-commands]

# Create container user
RUN adduser --disabled-password --home /home/container container

# Set user and environment
USER container
ENV USER=container HOME=/home/container

# Set working directory
WORKDIR /home/container

# Copy entrypoint script
COPY ./entrypoint.sh /entrypoint.sh

# Set entrypoint
CMD ["/bin/bash", "/entrypoint.sh"]

Example: Java Application

# ----------------------------------
# FeatherPanel Java Dockerfile
# Environment: Java 17
# Minimum Panel Version: 2.0.0
# ----------------------------------
FROM openjdk:17-jdk-alpine

MAINTAINER FeatherPanel Team, <[email protected]>

# Install dependencies
RUN apk add --no-cache --update \
    curl \
    ca-certificates \
    openssl \
    git \
    tar \
    bash \
    sqlite \
    fontconfig \
    && rm -rf /var/cache/apk/*

# Create container user
RUN adduser --disabled-password --home /home/container container

# Set user and environment
USER container
ENV USER=container HOME=/home/container

# Set working directory
WORKDIR /home/container

# Copy entrypoint script
COPY ./entrypoint.sh /entrypoint.sh

# Set entrypoint
CMD ["/bin/bash", "/entrypoint.sh"]

Example: Node.js Application

# ----------------------------------
# FeatherPanel Node.js Dockerfile
# Environment: Node.js 18
# Minimum Panel Version: 2.0.0
# ----------------------------------
FROM node:18-alpine

MAINTAINER FeatherPanel Team, <[email protected]>

# Install dependencies
RUN apk add --no-cache --update \
    curl \
    ca-certificates \
    openssl \
    git \
    tar \
    bash \
    python3 \
    make \
    g++ \
    && rm -rf /var/cache/apk/*

# Create container user
RUN adduser --disabled-password --home /home/container container

# Set user and environment
USER container
ENV USER=container HOME=/home/container

# Set working directory
WORKDIR /home/container

# Copy entrypoint script
COPY ./entrypoint.sh /entrypoint.sh

# Set entrypoint
CMD ["/bin/bash", "/entrypoint.sh"]

Example: Python Application

# ----------------------------------
# FeatherPanel Python Dockerfile
# Environment: Python 3.11
# Minimum Panel Version: 2.0.0
# ----------------------------------
FROM python:3.11-alpine

MAINTAINER FeatherPanel Team, <[email protected]>

# Install dependencies
RUN apk add --no-cache --update \
    curl \
    ca-certificates \
    openssl \
    git \
    tar \
    bash \
    build-base \
    && rm -rf /var/cache/apk/*

# Create container user
RUN adduser --disabled-password --home /home/container container

# Set user and environment
USER container
ENV USER=container HOME=/home/container

# Set working directory
WORKDIR /home/container

# Copy entrypoint script
COPY ./entrypoint.sh /entrypoint.sh

# Set entrypoint
CMD ["/bin/bash", "/entrypoint.sh"]

Creating the Entrypoint Script

Basic Entrypoint Script

#!/bin/bash
cd /home/container

# Output current version (optional)
[version-command]

# Replace startup variables
MODIFIED_STARTUP=`eval echo $(echo ${STARTUP} | sed -e 's/{{/${/g' -e 's/}}/}/g')`
echo ":/home/container$ ${MODIFIED_STARTUP}"

# Run the server
${MODIFIED_STARTUP}

Java Application Entrypoint

#!/bin/bash
cd /home/container

# Output Current Java Version
java -version

# Replace Startup Variables
MODIFIED_STARTUP=`eval echo $(echo ${STARTUP} | sed -e 's/{{/${/g' -e 's/}}/}/g')`
echo ":/home/container$ ${MODIFIED_STARTUP}"

# Run the Server
${MODIFIED_STARTUP}

Node.js Application Entrypoint

#!/bin/bash
cd /home/container

# Output Current Node.js Version
node --version
npm --version

# Install dependencies if package.json exists
if [ -f package.json ]; then
    echo "Installing dependencies..."
    npm install
fi

# Replace Startup Variables
MODIFIED_STARTUP=`eval echo $(echo ${STARTUP} | sed -e 's/{{/${/g' -e 's/}}/}/g')`
echo ":/home/container$ ${MODIFIED_STARTUP}"

# Run the Server
${MODIFIED_STARTUP}

Python Application Entrypoint

#!/bin/bash
cd /home/container

# Output Current Python Version
python3 --version
pip3 --version

# Install dependencies if requirements.txt exists
if [ -f requirements.txt ]; then
    echo "Installing dependencies..."
    pip3 install -r requirements.txt
fi

# Replace Startup Variables
MODIFIED_STARTUP=`eval echo $(echo ${STARTUP} | sed -e 's/{{/${/g' -e 's/}}/}/g')`
echo ":/home/container$ ${MODIFIED_STARTUP}"

# Run the Server
${MODIFIED_STARTUP}

Game Server Entrypoint

#!/bin/bash
cd /home/container

# Output Server Information
echo "Starting game server..."
echo "Memory: ${SERVER_MEMORY}MB"
echo "Port: ${SERVER_PORT}"

# Create necessary directories
mkdir -p logs
mkdir -p config
mkdir -p worlds

# Replace Startup Variables
MODIFIED_STARTUP=`eval echo $(echo ${STARTUP} | sed -e 's/{{/${/g' -e 's/}}/}/g')`
echo ":/home/container$ ${MODIFIED_STARTUP}"

# Run the Server
${MODIFIED_STARTUP}

Building and Testing

Building the Image

# Build the image
docker build -t your-username/your-image:latest .

# Tag for registry
docker tag your-username/your-image:latest your-registry.com/your-username/your-image:latest

# Push to registry
docker push your-registry.com/your-username/your-image:latest

Testing the Image

# Test the image locally
docker run -it --rm \
  -e STARTUP="echo 'Hello World'" \
  -e SERVER_MEMORY="1024" \
  -e SERVER_PORT="25565" \
  your-username/your-image:latest

# Test with actual application
docker run -it --rm \
  -e STARTUP="java -version" \
  -e SERVER_MEMORY="1024" \
  -e SERVER_PORT="25565" \
  -v $(pwd)/test-data:/home/container \
  your-username/your-image:latest

Testing with FeatherPanel

Create a test spell using your image
Create a test server with the spell
Start the server and monitor logs
Verify functionality works as expected
Test stop/start procedures

Advanced Configuration

Multi-stage Builds

For complex applications, use multi-stage builds to reduce image size:

# Build stage
FROM node:18-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production

# Runtime stage
FROM node:18-alpine
MAINTAINER FeatherPanel Team, <[email protected]>

# Install runtime dependencies
RUN apk add --no-cache --update \
    curl \
    ca-certificates \
    openssl \
    git \
    tar \
    bash \
    && rm -rf /var/cache/apk/*

# Create container user
RUN adduser --disabled-password --home /home/container container

# Set user and environment
USER container
ENV USER=container HOME=/home/container

# Set working directory
WORKDIR /home/container

# Copy built application
COPY --from=builder --chown=container:container /app/node_modules ./node_modules

# Copy entrypoint script
COPY ./entrypoint.sh /entrypoint.sh

# Set entrypoint
CMD ["/bin/bash", "/entrypoint.sh"]

Custom Installation Scripts

For applications that need custom installation:

# Copy installation script
COPY ./install.sh /install.sh
RUN chmod +x /install.sh

# Run installation
RUN /install.sh

# Clean up
RUN rm /install.sh

Environment-specific Configuration

# Set environment variables
ENV NODE_ENV=production
ENV PYTHONUNBUFFERED=1
ENV JAVA_OPTS="-Xms128M -Xmx512M"

# Set timezone
ENV TZ=UTC
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone

Security Best Practices

User Security

# Create non-root user
RUN adduser --disabled-password --home /home/container container

# Set proper permissions
RUN chown -R container:container /home/container
RUN chmod 755 /home/container

# Switch to non-root user
USER container

File Permissions

# Set proper file permissions
RUN chmod +x /entrypoint.sh
RUN chmod 755 /home/container

# Remove sensitive files
RUN rm -rf /tmp/* /var/tmp/*

Network Security

# Expose only necessary ports
EXPOSE 25565

# Set network policies
RUN echo "net.ipv4.ip_forward=0" >> /etc/sysctl.conf

Optimization Tips

Image Size Optimization

# Use Alpine Linux base images
FROM openjdk:17-jdk-alpine

# Combine RUN commands
RUN apk add --no-cache --update \
    curl \
    ca-certificates \
    openssl \
    && rm -rf /var/cache/apk/*

# Remove unnecessary files
RUN rm -rf /tmp/* /var/tmp/* /var/cache/apk/*

Build Optimization

# Use .dockerignore file
# .dockerignore
node_modules
npm-debug.log
.git
.gitignore
README.md
Dockerfile
.dockerignore

# Copy files in optimal order
COPY package*.json ./
RUN npm ci --only=production
COPY . .

Runtime Optimization

# Set optimal environment variables
ENV NODE_OPTIONS="--max-old-space-size=512"
ENV PYTHONUNBUFFERED=1
ENV JAVA_OPTS="-Xms128M -Xmx512M"

Common Issues and Solutions

Permission Issues

# Fix permission issues
RUN chown -R container:container /home/container
RUN chmod -R 755 /home/container

Missing Dependencies

# Install all required dependencies
RUN apk add --no-cache --update \
    curl \
    ca-certificates \
    openssl \
    git \
    tar \
    bash \
    python3 \
    make \
    g++ \
    && rm -rf /var/cache/apk/*

Entrypoint Script Issues

#!/bin/bash
# Ensure script is executable
chmod +x /entrypoint.sh

# Handle errors gracefully
set -e
set -o pipefail

# Add error handling
if [ $? -ne 0 ]; then
    echo "Error: Failed to start server"
    exit 1
fi

Distribution

Docker Registry

# Build and tag
docker build -t your-registry.com/your-username/your-image:latest .
docker tag your-registry.com/your-username/your-image:latest your-registry.com/your-username/your-image:v1.0.0

# Push to registry
docker push your-registry.com/your-username/your-image:latest
docker push your-registry.com/your-username/your-image:v1.0.0

GitHub Container Registry

# Login to GitHub Container Registry
echo $GITHUB_TOKEN | docker login ghcr.io -u USERNAME --password-stdin

# Build and push
docker build -t ghcr.io/your-username/your-image:latest .
docker push ghcr.io/your-username/your-image:latest

Docker Hub

# Login to Docker Hub
docker login

# Build and push
docker build -t your-username/your-image:latest .
docker push your-username/your-image:latest

Best Practices

Image Design

Use official base images when possible
Minimize image size with multi-stage builds
Follow security best practices (non-root user)
Include necessary dependencies only
Document image requirements clearly

Build Process

Use .dockerignore to exclude unnecessary files
Combine RUN commands to reduce layers
Cache dependencies for faster builds
Test builds in clean environments
Version your images with semantic versioning

Runtime

Handle errors gracefully in entrypoint scripts
Provide useful logging for debugging
Set appropriate environment variables
Optimize for container environment
Test thoroughly before distribution

This comprehensive guide should help you create robust, secure, and efficient Docker images for FeatherPanel spells that provide reliable server management and optimal performance.

Creating Custom Docker Images

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