Error: Cannot find module 'commander'

Install commander globally.

sudo npm install commander -g

• This will install commander module under/usr/lib/node_modules/.

Uninstalling sails and reinstalling with 'sudo' resolved it.

npm uninstall sails -g

sudo npm install sails -g

Most likely commander is missing from package.json. Install it and add it to package.json by doing:

npm install commander --save