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Overview

SSH Portfolio can be configured using environment variables to customize runtime behavior without modifying code or rebuilding the application.

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Available Environment Variables

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SSH_PORT

Controls which port the SSH server listens on.
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SSH_PORT
string
default:"2222"
The port number for the SSH server to bind to.
Implementation (main.go:27-29): 
port := "2222"
if p := os.Getenv("SSH_PORT"); p != "" {
    port = p
}
Usage: 
SSH_PORT=3000 ./ssh-portfolio

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Configuration Files

In addition to environment variables, SSH Portfolio uses configuration files:

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config.yaml

The application loads config.yaml from the working directory (main.go:31-34): 
cfg, err := config.Load("config.yaml")
if err != nil {
    log.Fatalf("Failed to load config: %v", err)
}
Location: Must be in the same directory as the binary or specified via mount in Docker.

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SSH Host Keys

SSH host keys are loaded from a hardcoded path (main.go:38): 
wish.WithHostKeyPath(".ssh/id_ed25519"),
Default path: .ssh/id_ed25519 (relative to working directory)
The host key path is not currently configurable via environment variables. It must exist at .ssh/id_ed25519 relative to the working directory.

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Server Configuration

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Host Address

The server binds to all interfaces by default (main.go:25): 
host := "0.0.0.0"
Default: 0.0.0.0 (all interfaces)
The host address is hardcoded and not configurable via environment variables. To bind to a specific interface, you would need to modify the source code.

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Default Port

When SSH_PORT is not set, the server uses port 2222 (main.go:26): 
port := "2222"
Default: 2222

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Address Binding

The host and port are combined using (main.go:37): 
wish.WithAddress(net.JoinHostPort(host, port)),
This creates the full address like 0.0.0.0:2222.

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Configuration Examples

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Development Setup

Run locally on a high port: 
SSH_PORT=2222 ./ssh-portfolio
Connect with: 
ssh localhost -p 2222

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Production Setup

Run on standard SSH port (requires root or capabilities): 
SSH_PORT=22 ./ssh-portfolio
Connect with: 
ssh yourserver.com

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Docker Development

Map container port 22 to host port 2222: 
docker run -d \
  -p 2222:22 \
  -e SSH_PORT=22 \
  -v $(pwd)/config.yaml:/app/config.yaml \
  -v ssh-keys:/app/.ssh \
  ssh-portfolio:latest

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Docker Production

Run on standard SSH port: 
services:
  ssh-portfolio:
    build: .
    ports:
      - "22:22"
    environment:
      - SSH_PORT=22
    volumes:
      - ./config.yaml:/app/config.yaml
      - ssh-keys:/app/.ssh
    restart: unless-stopped

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systemd Service

Configure via systemd unit file: 
[Service]
Type=simple
User=portfolio
WorkingDirectory=/opt/ssh-portfolio
Environment="SSH_PORT=2222"
ExecStart=/opt/ssh-portfolio/ssh-portfolio
Restart=always

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Multiple Instances

Run multiple instances on different ports: 
SSH_PORT=2222 ./ssh-portfolio &
Each instance must have its own working directory with separate config.yaml and .ssh/id_ed25519 files.

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Override Hierarchy

Configuration is loaded in this order:
  1. Code defaults - Hardcoded in main.go
    • Host: 0.0.0.0
    • Port: 2222
    • Config file: config.yaml
    • SSH keys: .ssh/id_ed25519
  2. Environment variables - Override defaults
    • SSH_PORT - Overrides default port
  3. Command-line flags - Not currently implemented

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Default Values Summary

SettingDefault ValueConfigurableMethod
Host0.0.0.0NoHardcoded
Port2222YesSSH_PORT
Config fileconfig.yamlNoHardcoded
SSH key path.ssh/id_ed25519NoHardcoded

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Validation and Errors

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Missing Configuration File

If config.yaml is not found: 
Failed to load config: open config.yaml: no such file or directory
Solution: Ensure config.yaml exists in the working directory.

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Missing SSH Host Keys

If .ssh/id_ed25519 is not found, the server will attempt to generate keys automatically. If generation fails: 
Failed to create SSH server: unable to load or generate host keys
Solution: Manually generate keys with: 
mkdir -p .ssh
ssh-keygen -t ed25519 -f .ssh/id_ed25519 -N ""

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Invalid Port Number

If SSH_PORT contains an invalid port: 
Server error: listen tcp: address 99999: invalid port
Solution: Use a valid port number (1-65535). Ports below 1024 require root privileges.

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Port Already in Use

If the port is already bound: 
Server error: listen tcp :2222: bind: address already in use
Solution: Choose a different port or stop the conflicting service.

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Environment Files

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Using .env Files

Create a .env file for local development: 
# .env
SSH_PORT=2222
Load it before running: 
export $(cat .env | xargs)
./ssh-portfolio
Or use a tool like direnv: 
# .envrc
export SSH_PORT=2222

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Docker .env File

Docker Compose automatically loads .env: 
# .env
SSH_PORT=3000

# docker-compose.yml
services:
  ssh-portfolio:
    build: .
    ports:
      - "${SSH_PORT}:${SSH_PORT}"
    environment:
      - SSH_PORT=${SSH_PORT}

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Security Considerations

Never commit .env files containing sensitive information to version control. Add .env to your .gitignore.

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Sensitive Values

While SSH Portfolio currently doesn’t use sensitive environment variables, follow these best practices:
  • Use restrictive file permissions: chmod 600 .env
  • Store secrets in proper secret management systems
  • Rotate SSH host keys periodically
  • Monitor environment variable access in logs

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Next Steps

Docker Deployment

Deploy with Docker

Manual Deployment

Deploy from source

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