1.-npm install gulp -g
You need to unlock permissions in your home directory
-
sudo chown -R `whoami` ~/.npm
You also need write permissions to the node_modules directory, like Xilo says, so if it still isn't working, try: -
sudo chown -R `whoami` /usr/local/lib/node_modules
If you are still seeing errors, you may also need to correct /usr/local permissions: