sudo apt-get install node-less

sudo apt-get install npm

sudo npm install -g less less-plugin-clean-css

sudo ln -s /usr/bin/nodejs /usr/bin/node

OR

sudo apt-get install curlcurl -sL 

https://deb.nodesource.com/setup_0.12

 | sudo bash -sudo apt-get install nodejssudo npm install -g less-plugin-clean-css less

OR (99.99% below should work):

[17:07:11] Mustufa Rangwala - Odoo / OpenERP: sudo apt-get install curl

curl -sL https://deb.nodesource.com/setup_0.12 | sudo bash -

sudo apt-get install nodejs

sudo npm install -g less-plugin-clean-css less