This script setup ssh key to connect to server (to run on your local machine)

vps-setup-ssh-key.sh

#!/bin/bash

# Default values
PORT=22
WITH_PASSPHRASE=false

# Parse CLI arguments
while [[ "$#" -gt 0 ]]; do
  case $1 in
    --server-name)
      SERVER_NAME="$2"
      shift 2
      ;;
    --host)
      HOST_NAME="$2"
      shift 2
      ;;
    --user)
      USER="$2"
      shift 2
      ;;
    --port)
      PORT="$2"
      shift 2
      ;;
    --with-passphrase)
      WITH_PASSPHRASE=true
      shift 1
      ;;
    *)
      echo "❌ Unknown option: $1"
      exit 1
      ;;
  esac
done

# Validate required fields
if [[ -z "$SERVER_NAME" || -z "$HOST_NAME" || -z "$USER" ]]; then
  echo "❌ Usage: $0 --server-name NAME --host IP --user USER [--port 22] [--with-passphrase]"
  exit 1
fi

# Define paths
SSH_DIR="$HOME/.ssh"
CONFIG_FILE="$SSH_DIR/config"
KEY_PATH="$SSH_DIR/id_${SERVER_NAME}"

# Ensure .ssh directory and config file exist
mkdir -p "$SSH_DIR"
touch "$CONFIG_FILE"
chmod 700 "$SSH_DIR"
chmod 600 "$CONFIG_FILE"

# Generate SSH key if it doesn't exist
if [[ -f "$KEY_PATH" ]]; then
  echo "⚠️ SSH key $KEY_PATH already exists. Reusing it."
else
  echo "🔐 Generating SSH key..."
  if [ "$WITH_PASSPHRASE" = true ]; then
    ssh-keygen -t ed25519 -f "$KEY_PATH"
  else
    ssh-keygen -t ed25519 -f "$KEY_PATH" -N ""
  fi
fi

# Add entry to ~/.ssh/config if not already present
if ! grep -q "Host $SERVER_NAME" "$CONFIG_FILE"; then
  echo "📝 Adding server config to ~/.ssh/config..."
  cat >> "$CONFIG_FILE" <<EOF

Host $SERVER_NAME
  HostName $HOST_NAME
  User $USER
  Port $PORT
  IdentityFile $KEY_PATH
  IdentitiesOnly yes
EOF
else
  echo "✅ Server $SERVER_NAME is already in ~/.ssh/config"
fi

# Copy public key to remote server
echo "📤 Copying public key to $USER@$HOST_NAME..."
ssh-copy-id -i "${KEY_PATH}.pub" -p "$PORT" "$USER@$HOST_NAME"

echo "✅ Done! You can now connect with: ssh $SERVER_NAME"