Installing Claude Code in Existing Linux Containers (Battle-Tested Guide)

Table of Contents

1. Claude Code Overview
2. Accessing Running Containers
3. System Environment Check
4. Node.js Installation (NVM Recommended)
5. Claude Code Installation
6. Authentication Setup
7. Usage
8. Troubleshooting
9. Verified Installation Script

Claude Code Overview

Claude Code is a terminal-based AI coding tool developed by Anthropic that provides:

• Edit files and fix bugs across your entire codebase
• Answer questions about code architecture and logic
• Run and fix tests, linting, and other commands
• Manage Git workflows (resolve merge conflicts, create PRs, etc.)
• Explore docs and resources through web search

System Requirements: Node.js 18+ (Recommended: 20+ LTS)

Accessing Running Containers

1. Check Container List

# Check running containers
docker ps

# Example output:
CONTAINER ID   IMAGE     COMMAND       CREATED        STATUS        PORTS     NAMES
abc123def456   ubuntu    "/bin/bash"   2 hours ago    Up 2 hours              my-dev-container

2. Access Container

# Access container using container name
docker exec -it my-dev-container /bin/bash

# Or using container ID
docker exec -it abc123def456 /bin/bash

# If bash is not available, try sh
docker exec -it my-dev-container /bin/sh

System Environment Check

Once inside the container, let’s check what we’re working with:

# Check OS version
cat /etc/os-release

# Check available package managers
which apt-get    # Debian/Ubuntu
which yum        # RHEL/CentOS
which apk        # Alpine

# Check if curl/wget is available
which curl
which wget

# Check current shell
echo $SHELL

Node.js Installation (NVM Recommended)

Why NVM?

• Easy version management
• No root permissions needed
• Works in most container environments

Install NVM and Node.js

# Install NVM
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.0/install.sh | bash

# Reload shell configuration
source ~/.bashrc
# or
export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"

# Install latest LTS Node.js
nvm install --lts
nvm use --lts

# Verify installation
node --version
npm --version

Alternative: Direct Node.js Installation

For Ubuntu/Debian:

# Update package list
apt-get update

# Install Node.js
curl -fsSL https://deb.nodesource.com/setup_20.x | bash -
apt-get install -y nodejs

# Verify
node --version
npm --version

For Alpine Linux:

# Install Node.js
apk add --no-cache nodejs npm

# Verify
node --version
npm --version

Claude Code Installation

Method 1: NPM Installation

# Install Claude Code globally
npm install -g @anthropic-ai/claude-code

# Verify installation
claude --version

Method 2: Direct Download (if npm fails)

# Download and install
curl -fsSL https://claude.ai/install.sh | sh

# Add to PATH if needed
export PATH="$HOME/.claude/bin:$PATH"
echo 'export PATH="$HOME/.claude/bin:$PATH"' >> ~/.bashrc

Authentication Setup

1. Get API Key

1. Visit Claude.ai
2. Sign in to your account
3. Go to Settings → API Keys
4. Generate a new API key

2. Configure Authentication

# Set up authentication
claude auth login

# Or set environment variable
export ANTHROPIC_API_KEY="your-api-key-here"
echo 'export ANTHROPIC_API_KEY="your-api-key-here"' >> ~/.bashrc

3. Verify Authentication

# Test connection
claude --test-auth

Usage

Basic Commands

# Start interactive session
claude

# Analyze specific files
claude analyze src/main.js

# Fix issues in files
claude fix src/

# Generate code
claude generate "create a REST API endpoint for user authentication"

# Help with Git
claude git "help me resolve merge conflicts"

Example Interactive Session

$ claude
Claude Code v1.0.0
Type 'help' for available commands or start describing what you'd like to do.

> Can you help me fix the TypeScript errors in this project?
I'll analyze your TypeScript files and help fix the errors. Let me start by examining your project structure...

[Claude analyzes files and provides fixes]

Troubleshooting

Common Issues and Solutions

1. Permission Denied Errors

# If you get permission errors with npm
npm config set prefix ~/.npm-global
export PATH=~/.npm-global/bin:$PATH
echo 'export PATH=~/.npm-global/bin:$PATH' >> ~/.bashrc

2. Node.js Version Issues

# Check Node version
node --version

# Update to latest LTS if needed
nvm install --lts
nvm use --lts

3. Network/Firewall Issues

# Test internet connectivity
curl -I https://api.anthropic.com

# Check if proxy is needed
echo $HTTP_PROXY
echo $HTTPS_PROXY

4. Container Environment Issues

# Some containers might need additional packages
apt-get install -y ca-certificates curl gnupg

# For Alpine
apk add --no-cache ca-certificates curl

Debug Mode

# Enable debug logging
export CLAUDE_DEBUG=1
claude --version

Verified Installation Script

Here’s a battle-tested script that handles most common scenarios:

#!/bin/bash
set -e

echo "🚀 Installing Claude Code in Container..."

# Detect OS
if command -v apt-get >/dev/null 2>&1; then
    OS="ubuntu"
    PACKAGE_MANAGER="apt"
elif command -v yum >/dev/null 2>&1; then
    OS="centos"
    PACKAGE_MANAGER="yum"
elif command -v apk >/dev/null 2>&1; then
    OS="alpine"
    PACKAGE_MANAGER="apk"
else
    echo "❌ Unsupported OS"
    exit 1
fi

echo "📊 Detected OS: $OS"

# Install dependencies
echo "📦 Installing dependencies..."
case $PACKAGE_MANAGER in
    "apt")
        apt-get update
        apt-get install -y curl ca-certificates gnupg
        ;;
    "yum")
        yum install -y curl ca-certificates
        ;;
    "apk")
        apk add --no-cache curl ca-certificates
        ;;
esac

# Install Node.js via NVM
echo "📦 Installing Node.js..."
if ! command -v node >/dev/null 2>&1; then
    curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.0/install.sh | bash
    export NVM_DIR="$HOME/.nvm"
    [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
    nvm install --lts
    nvm use --lts
else
    echo "✅ Node.js already installed: $(node --version)"
fi

# Install Claude Code
echo "🤖 Installing Claude Code..."
npm install -g @anthropic-ai/claude-code

# Verify installation
echo "✅ Verifying installation..."
claude --version

echo "🎉 Installation complete!"
echo "💡 Next steps:"
echo "   1. Run 'claude auth login' to authenticate"
echo "   2. Run 'claude' to start using Claude Code"

Save and Run the Script

# Save the script
cat > install-claude.sh << 'EOF'
[paste the script above]
EOF

# Make executable and run
chmod +x install-claude.sh
./install-claude.sh

Final Notes

Best Practices

1. Always test in a non-production container first
2. Keep your API key secure - never hardcode it in scripts
3. Use environment variables for configuration
4. Regularly update Claude Code for new features and fixes

Container Persistence

Remember that changes made inside a container will be lost when the container is removed unless:

• You commit the container to a new image
• You use volumes to persist data
• You rebuild your Dockerfile to include these installations

Quick Container Setup for Development

# Create a development container with Claude Code pre-installed
docker run -it --name claude-dev ubuntu:22.04 /bin/bash

# Inside container, run the installation script
# Then commit the container
docker commit claude-dev my-claude-dev:latest

Happy coding with Claude! 🚀 This guide has been tested on Ubuntu, Alpine, and CentOS containers.