Node and npm should be installed via the package manager, its better this way. Follow this guide: Installing-Node.js-via-package-manager
If you already have node and npm installed, check that it is installed correctly:
apt-cache search ^nodejs$
If that does not return "nodejs - Node.js ..." you might want to consider deleting the current install and re-installing. Feel free to see me (Matt) for help installing on Ubuntu or other Linux distros.
You should not need to be sudo to npm install
!!!
If you are getting permission errors and it is suggestion running as admin/root, don't do it. There is a better way!
Run the following commands, trust me...
sudo rm -rf <PATH TO SITE>/node_modules
sudo rm -rf ~/.npm
sudo rm -rf ~/tmp/npm-*
sudo chmod <USER NAME> ~/tmp
chmod u+rw ~/tmp
sudo apt-get install g++