Linux: パッケージ管理 — apt / dpkg / snapとソフトウェアインストール

sudo apt update
sudo apt install nginx -y

# Update package source lists
sudo apt update

# Upgrade all installed packages
sudo apt upgrade -y

> 💡 ヒント：`apt update && apt upgrade -y`はシステム保守の黄金コンビ — `update`がパッケージソースリストを更新し、`upgrade`がインストール済みパッケージをアップグレードします。新しいソフトをインストールする前に必ず`update`を実行してください。そうしないと最新版が見つからない場合があります。

# Install software
sudo apt install nginx -y
sudo apt install curl wget git vim -y    # Install multiple at once

# Remove software
sudo apt remove nginx                    # Keep config files
sudo apt purge nginx                     # Delete config files too

# Search
apt search "web server"
apt show nginx                           # View package info

# Clean up
sudo apt autoremove                      # Remove unneeded dependencies
sudo apt autoclean                       # Clean downloaded cache

# Install a local .deb file
sudo dpkg -i package.deb

# If dependencies are missing, fix with apt
sudo apt install -f

# View installed packages
dpkg -l | grep nginx
dpkg -L nginx                           # View files installed by the package

# Remove
sudo dpkg -r package_name               # Remove
sudo dpkg -P package_name               # Purge (including config files)

# Package source list
cat /etc/apt/sources.list

# Add a PPA (Personal Package Archive)
sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt update
sudo apt install python3.12

# Ubuntu software source priority order
# 1. /etc/apt/sources.list
# 2. /etc/apt/sources.list.d/*.list

# snap (built into Ubuntu)
snap find "code"                         # Search
sudo snap install code --classic         # Install VS Code
sudo snap install lxd                    # Install LXD
sudo snap refresh                        # Update all snaps
sudo snap remove code                    # Remove

# snap features: auto-update, sandbox isolation, cross-distribution

# Python
pip install requests                     # Install Python package
pip install -r requirements.txt          # Install from file
pip list                                 # List installed packages
pip uninstall requests                   # Uninstall
pip freeze > requirements.txt            # Export dependencies

# Node.js
npm install express                      # Install package
npm install -g typescript                # Global install
npm list                                 # List installed packages
npx create-react-app my-app              # Run without installing

# Rust
cargo install ripgrep                    # Install tool
cargo add serde                          # Add dependency to project

# 1. Update package sources
sudo apt update

# 2. Install common dev tools
sudo apt install -y build-essential curl wget git vim htop

# 3. Search for a package
apt search "text editor" | grep -i "vim\|nano"

# 4. View package info
apt show htop

# 5. Remove
sudo apt remove htop
sudo apt autoremove    # Clean up unneeded dependencies

# Download VS Code .deb package
wget https://code.visualstudio.com/sha/download?build=stable&os=linux-deb-x64 -O code.deb

# Install
sudo dpkg -i code.deb

# If dependency issues are reported, fix them
sudo apt install -f

# View files installed by VS Code
dpkg -L code | head -20

# Ubuntu 22.04 default is Python 3.10; to install Python 3.12, you need a PPA
sudo add-apt-repository ppa:deadsnakes/ppa -y
sudo apt update
sudo apt install -y python3.12 python3.12-venv python3.12-distutils

# Verify
python3.12 --version

# Install Flask web framework
pip install flask

# Create a dependency list
pip freeze > requirements.txt

# Install the same dependencies on another machine
pip install -r requirements.txt

# Install to user directory (no sudo needed)
pip install --user black

# View which directories nginx was installed to
dpkg -L nginx | head -10

# View nginx config files
dpkg -L nginx | grep -E "\.conf$"

# Find which package a command belongs to
dpkg -S /usr/bin/htop
# htop: /usr/bin/htop

# Reverse — find which package a file belongs to
dpkg -S /etc/nginx/nginx.conf
# nginx: /etc/nginx/nginx.conf

#!/bin/bash
# setup-web-env.sh - Set up a Web development environment from scratch

set -e

echo "=== Setting Up Web Development Environment ==="

# 1. Update system
echo ">>> Updating package sources..."
sudo apt update
sudo apt upgrade -y

# 2. Install basic tools
echo ">>> Installing basic tools..."
sudo apt install -y build-essential curl wget git vim htop net-tools

# 3. Install Nginx
echo ">>> Installing Nginx..."
sudo apt install -y nginx
sudo systemctl enable nginx
sudo systemctl start nginx

# 4. Install Node.js
echo ">>> Installing Node.js 20..."
curl -fsSL https://deb.nodesource.com/setup_20.x | sudo -E bash -
sudo apt install -y nodejs

> ⚠️ 警告：`curl | bash`パターン（インターネットからスクリプトをダウンロードして直接実行）はサプライチェーン攻撃のリスクがあります — サーバーが侵害されたりDNSがハイジャックされた場合、悪意のあるコードが実行される可能性があります。本番サーバーでは、スクリプトを先にダウンロードして内容を確認してから実行するか、ディストリビューションの公式リポジトリを優先してください。

# 5. Install Python 3 + pip
echo ">>> Installing Python 3..."
sudo apt install -y python3 python3-pip python3-venv

# 6. Install Docker
echo ">>> Installing Docker..."
curl -fsSL https://get.docker.com | sudo sh
sudo usermod -aG docker $USER

# 7. Verify
echo ""
echo "=== Environment Verification ==="
echo "Nginx: $(nginx -v 2>&1)"
echo "Node.js: $(node --version)"
echo "npm: $(npm --version)"
echo "Python: $(python3 --version)"
echo "Git: $(git --version)"
echo "Docker: $(docker --version)"

echo ""
echo "✅ Environment setup complete! Some changes (like Docker) require re-login to take effect."