Refactor Dockerfile to remove package upgrade during build and update README for clarity and structure

Author: idvoretskyi

.devcontainer/Dockerfile

@@ -2,7 +2,6 @@ FROM mcr.microsoft.com/devcontainers/base:ubuntu-24.04
 
 # hadolint ignore=DL3008
 RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \
-    && apt-get -y upgrade --no-install-recommends \
     && apt-get -y install --no-install-recommends \
         curl \
         wget \

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2025 Ihor Dvoretskyi
+Copyright (c) 2026 Ihor Dvoretskyi
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -3,59 +3,73 @@
 [![CI](https://github.com/idvoretskyi/dev/actions/workflows/ci.yml/badge.svg)](https://github.com/idvoretskyi/dev/actions/workflows/ci.yml)
 [![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/idvoretskyi/dev)
 
-This repository serves as an optimized GitHub Codespaces template for general development workflows.
+This repository provides a lean development container template for GitHub
+Codespaces and local VS Code Dev Containers.
 
 ## Features
 
-- Base image: Ubuntu 24.04
-- Essential development tools:
-  - Python 3.12 with pip
-  - Node.js LTS with npm
-  - Git (OS-provided)
+- Ubuntu 24.04 base image
+- Single-image devcontainer build based on `.devcontainer/Dockerfile`
+- Core tooling for general development work:
+  - Python 3 with `venv` and `pip`
+  - Node.js LTS with `npm`
   - Docker-in-Docker with Docker Compose v2
   - GitHub CLI
-  - Claude Code CLI
-  - Zsh with common utilities
-  - Build essentials (gcc, make, etc.)
+  - Claude Code CLI installed in `postCreateCommand`
+  - Zsh and common shell utilities
+  - Build essentials (`gcc`, `make`, and related packages)
+  - SSH daemon support via the devcontainer feature
 - VS Code extensions:
-  - Claude Dev (Anthropic)
-  - Python language support
-  - Docker support
-  - GitHub Copilot
-  - YAML support
+  - Anthropic Claude Code
+  - Python and Pylance
+  - Docker
+  - GitHub Copilot and Copilot Chat
+  - YAML
 
 ## Performance Optimizations
 
 The devcontainer balances speed with operability:
 
-- Includes essential tools: Python, Node.js, Docker, Git, GitHub CLI, Claude Code CLI
-- Disabled package upgrades during build
-- Removed heavy features (kubectl, helm, minikube, sshd)
-- Uses OS-provided Git for faster builds
-- Uses OS-provided Python (precompiled) for faster setup
-- Installs Claude Code CLI via npm in postCreateCommand
-- Core VS Code extensions only
+- Keeps the image focused on core development tooling
+- Avoids full package upgrades during image build to reduce rebuild time
+- Uses the devcontainer feature set for Node.js, Git, Docker, GitHub CLI, and SSH
+- Uses Ubuntu's packaged Python runtime for a faster base setup
+- Installs Claude Code CLI in `postCreateCommand` instead of baking it into the image
+- Limits editor customizations to a small, broadly useful extension set
 
-Estimated startup time: 2-3 minutes
+Estimated startup time: 2-3 minutes, depending on feature downloads and
+network speed.
 
 ## Usage
 
 ### GitHub Codespaces
+
 1. Click "Code" button on the GitHub repository
 2. Select "Create codespace on main"
 3. Wait for the environment to build
 
 ### VS Code Local Dev Containers
+
 1. Clone this repository
 2. Open in VS Code
 3. Click "Reopen in Container" when prompted
 
+## Repository Structure
+
+- `.devcontainer/devcontainer.json`: main devcontainer definition, features,
+  VS Code extensions, and post-create validation command
+- `.devcontainer/Dockerfile`: minimal image customization for extra packages
+- `.github/workflows/ci.yml`: CI checks for Dockerfile linting, secret
+  scanning, image build, and devcontainer smoke testing
+
 ## Using as a Template
 
 ### Method 1: GitHub Template
+
 Click "Use this template" button to create a new repository
 
 ### Method 2: Copy Configuration
+
 ```bash
 cp -r .devcontainer /path/to/your/project/
 ```
@@ -75,7 +89,7 @@ Edit `.devcontainer/devcontainer.json` to add features or tools:
 }
 ```
 
-To add heavy tools like Kubernetes:
+To add heavier tooling when you actually need it:
 
 ```json
 {
@@ -89,6 +103,9 @@ To add heavy tools like Kubernetes:
 }
 ```
 
+If you add new features or packages, keep the CI workflow in sync with any new
+tooling expectations you want validated during the container smoke test.
+
 ## License
 
 This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.