Claude Code

Claude Code is the official command-line programming tool from Anthropic, powered by the Claude large language model. It works directly in your terminal to help you write code, analyze projects, and perform system administration tasks. It can understand the context of an entire codebase and directly read/write files and run commands, making it a powerful assistant for server-side development and operations.

System Requirements

• CentOS Stream 9 & 10 / AlmaLinux 9 & 10 / Rocky Linux 9 & 10
• Node.js 22 or higher; the current LTS is Node.js 24 (Node.js 20 reached EOL in 2026-04)
• Anthropic API key (obtain from console.anthropic.com)
• Network access to the Anthropic API

Installing Node.js

The Node.js version in the default EL repositories may be outdated (EL 9.8 / EL 10 currently ship Node.js 24 / 22 respectively). It is recommended to install the latest LTS version via the NodeSource repository.

Option 1: NodeSource Repository (Recommended)

# Install Node.js 24.x LTS
curl -fsSL https://rpm.nodesource.com/setup_24.x | sudo bash -
sudo dnf install -y nodejs

Option 2: dnf module (EL 9 only)

# List available Node.js versions
sudo dnf module list nodejs

# Enable and install Node.js 24
sudo dnf module enable nodejs:24 -y
sudo dnf install -y nodejs

Note

EL 10 no longer distributes modular content, so dnf module enable has no modules to enable (the command still exists but is deprecated). EL 10 official repositories ship Node.js 22 directly — run sudo dnf install nodejs. For a newer version (such as the current LTS 24), use the NodeSource repository from Option 1.

Verify the installation:

node --version
npm --version

Installing Claude Code

Install globally using npm:

npm install -g @anthropic-ai/claude-code

Verify the installation:

claude --version

Updating Claude Code

npm update -g @anthropic-ai/claude-code

Configuration

Setting the API Key

Running claude for the first time will guide you through authentication. You can also set it in advance via an environment variable:

# Temporary setting
export ANTHROPIC_API_KEY="sk-ant-xxxxx"

# Permanent setting (add to shell configuration file)
echo 'export ANTHROPIC_API_KEY="sk-ant-xxxxx"' >> ~/.bashrc
source ~/.bashrc

Using a Third-Party API Proxy

If you access the API through a proxy service, you can customize the API URL:

export ANTHROPIC_BASE_URL="https://your-proxy.example.com"
export ANTHROPIC_API_KEY="your-key"

Configuration Files

Claude Code’s configuration files are located in the ~/.claude/ directory. You can adjust settings through the interactive /config command or edit the configuration files directly:

ls -la ~/.claude/

Basic Usage

Starting an Interactive Session

Run directly in your project directory:

cd /path/to/your/project
claude

Once in the interactive interface, you can describe your needs in natural language.

Single Command Mode

Use the -p flag for a one-off question, suitable for scripting:

# Single question
claude -p "Explain the directory structure of this project"

# Analyze a specific file
claude -p "Analyze the configuration of /etc/nginx/nginx.conf. Are there any security concerns?"

Piping Input

# Analyze logs
journalctl -u nginx --since "1 hour ago" | claude -p "Analyze these logs. Are there any anomalies?"

# Review code
cat app.py | claude -p "Review the security of this code"

# Analyze system state
top -bn1 | claude -p "Analyze the system load"

Common Interactive Commands

In interactive mode, commands starting with / are built-in commands:

Command	Description
/help	Show help information
/config	Modify configuration
/clear	Clear conversation context
/compact	Compress conversation history to save tokens
/cost	View API usage for the current session

Practical Use Cases

Server Operations

You: Check the current disk usage and find the directories using the most space

You: Write a bash script that periodically cleans up log files older than 30 days in /var/log

Code Development

You: Create a Python Flask API with /health and /status endpoints

You: Read the current project code and write deployment steps for Rocky Linux

Configuration File Management

You: Generate an Nginx reverse proxy configuration that forwards /api requests to backend port 8080 with SSL enabled

You: Check the security configuration of /etc/ssh/sshd_config and provide hardening recommendations

MCP Servers

Claude Code supports MCP (Model Context Protocol) servers, which can extend its capabilities. MCP servers provide Claude Code with additional tools and data sources.

Configuring MCP Servers

Create a .mcp.json file in the project root directory:

{
  "mcpServers": {
    "filesystem": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-filesystem",
        "/opt/data"
      ]
    },
    "postgres": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-postgres",
        "postgresql://user:pass@localhost:5432/mydb"
      ]
    }
  }
}

You can also create a global MCP configuration in the ~/.claude/ directory.

Common MCP Servers

Add them via Claude Code interactive commands:

# Add filesystem MCP
claude mcp add filesystem npx -y @modelcontextprotocol/server-filesystem /opt/data

# Add PostgreSQL MCP
claude mcp add postgres npx -y @modelcontextprotocol/server-postgres "postgresql://user:pass@localhost/db"

# List configured MCP servers
claude mcp list

Tips for Using on EL Servers

Using with tmux

On a server, it is recommended to run Claude Code inside tmux to prevent session loss from SSH disconnections:

# Create a new tmux session
tmux new -s claude

# Run claude inside tmux
claude

# To detach, press Ctrl+B then D
# To reattach
tmux attach -t claude

Setting SELinux Context

If Claude Code needs to operate on files protected by SELinux:

# View the SELinux context of files
ls -Z /var/www/html/

# If files created by Claude Code have incorrect context, restore them
sudo restorecon -Rv /var/www/html/

Limiting Privileges

When using on production servers, it is recommended to run Claude Code as a regular user instead of root:

# Create a dedicated user
sudo useradd -m claude-user
sudo su - claude-user

# Install and run
npm install -g @anthropic-ai/claude-code
export ANTHROPIC_API_KEY="sk-ant-xxxxx"
claude

Offline or Restricted Network Environments

If the server accesses the internet through a proxy:

# Set HTTPS proxy
export HTTPS_PROXY="http://proxy.example.com:7890"
export ANTHROPIC_API_KEY="sk-ant-xxxxx"
claude

FAQ

npm Global Install Permission Issues

If you encounter permission errors:

# Option 1: Change the npm global directory
mkdir -p ~/.npm-global
npm config set prefix '~/.npm-global'
echo 'export PATH=~/.npm-global/bin:$PATH' >> ~/.bashrc
source ~/.bashrc
npm install -g @anthropic-ai/claude-code

# Option 2: Use sudo (not recommended)
sudo npm install -g @anthropic-ai/claude-code

Node.js Version Too Old

# Check version
node --version

# If below 22, upgrade Node.js following the instructions above

Connection Timeout

Check network connectivity and proxy settings:

# Test API connectivity (replace model with a currently available model ID; see Anthropic docs)
curl -v https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "content-type: application/json" \
  -H "anthropic-version: 2023-06-01" \
  -d '{"model":"claude-sonnet-4-5","max_tokens":10,"messages":[{"role":"user","content":"hi"}]}'