Migrating Python and Node.js Applications to a VDS

Migrating Python and Node.js applications has its own specifics: besides files and the database, you need to transfer the environment, install dependencies, and set up systemd services for autostart.

Migrating a Python/Django application

1. Pin down dependencies

># On the old server
source /path/to/venv/bin/activate
pip freeze > requirements.txt

# Transfer to the new server
git clone https://github.com/your/repo.git /var/www/myapp
# or rsync
rsync -avz /var/www/myapp/ root@new-server:/var/www/myapp/

2. Deploy on the new server

># Create the virtual environment
python3 -m venv /var/www/myapp/venv
source /var/www/myapp/venv/bin/activate

# Install dependencies
pip install -r requirements.txt

# Environment variables — transfer the .env file
scp old-server:/var/www/myapp/.env /var/www/myapp/.env

# Apply database migrations
python manage.py migrate

# Collect static files
python manage.py collectstatic --noinput

3. Setting up systemd for Django (Gunicorn)

># /etc/systemd/system/myapp.service
[Unit]
Description=Django App via Gunicorn
After=network.target

[Service]
User=www-data
WorkingDirectory=/var/www/myapp
EnvironmentFile=/var/www/myapp/.env
ExecStart=/var/www/myapp/venv/bin/gunicorn     --workers 3     --bind unix:/run/myapp.sock     myapp.wsgi:application

[Install]
WantedBy=multi-user.target

systemctl daemon-reload
systemctl enable --now myapp

Migrating a Node.js application

1. Pin down the Node.js version

># Check the version on the old server
node --version
npm --version

# Install nvm on the new server
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh | bash
source ~/.bashrc
nvm install 20  # Install the required version

2. Transfer and restore

># Transfer only the code (without node_modules!)
rsync -avz --exclude=node_modules   /var/www/nodeapp/ root@new-server:/var/www/nodeapp/

# Install dependencies on the new server
cd /var/www/nodeapp
npm ci  # clean install from package-lock.json

# Transfer .env
scp old-server:/var/www/nodeapp/.env /var/www/nodeapp/

3. PM2 for autostart

># Install PM2
npm install -g pm2

# Start the application
pm2 start app.js --name myapp

# Save the PM2 configuration (export from the old server)
# On the old server
pm2 save

# Transfer the config
scp old-server:~/.pm2/dump.pm2 ~/.pm2/
pm2 resurrect

# Set up autostart on reboot
pm2 startup
pm2 save

Nginx reverse proxy for Python/Node.js

># /etc/nginx/sites-available/myapp
server {
    listen 80;
    server_name myapp.example.com;

    location / {
        proxy_pass http://unix:/run/myapp.sock;  # Python/Gunicorn
        # or
        # proxy_pass http://localhost:3000;       # Node.js

        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}