The fix:

sudo apt-get install nodejs nodejs-legacy node-less
sudo apt-get install npm
sudo npm install -g less
sudo npm install -g less-plugin-clean-css
sudo ln -s /usr/local/bin/lessc /usr/bin/lessc
sudo ln -s /usr/bin/nodejs /usr/bin/node

After the fix you have 3 options (because a simply f5 to refresh or a server restart doesn't recompile your .less files):

1- Delete and/or Create a new Database

2- Install a module that add a new .less file to be compiled, like blog or website like was suggested here

3- Manually compile your .less files

Hi, install a Blogs module for fix the bug.

To all of you who are encountering this problem, it is due to a problem with an old version of nodejs (shows up especially in Ubuntu 12.04). To install a stable version we use Chris Lea's repo as follows:

• sudo apt-get install python-software-properties

• sudo apt-add-repository ppa:chris-lea/node.js

• sudo apt-get update

Then you install nodejs:

sudo apt-get install nodejs

You can then check version of nodejs using:

node -v

It should be at least greater than > 0.10

npm -v

Should return a version at least > 1.4

Then finally execute the following command, whick will update npm to a newer version as well as install the less plugin:

• sudo npm install -g npm

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

Enjoy, it worked for me after searching for long hours, enjoy, it worked for me after searching for long hours,

Mustafa

First Time that You see it... It's because You don't have lessc installed!

Once installed, You need to invalidate the bundle (installing any module which add less file) to generate again the bundle! 

This error shows because of two reasons

1. You don't install required packages and plug-ins on your ubuntu system or

2. Install packages and plug-ins are outdated

To overcome this problem try this commands on your ubuntu terminal

• sudo apt-get install curl

• curl -sL https://deb.nodesource.com/setup_0.10 | sudo bash -

• sudo apt-get install -y nodejs

• sudo npm install -g npm (to update npm)

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

It's not working here, What is with wkhtmltopdf?

before install blog run this :

 apt-get -y update && apt-get -y upgrade && apt-get -y install python python-egenix-mxdatetime python-dateutil python-pybabel python-openid python-feedparser python-lxml python-libxml2 python-libxslt1 python-psycopg2 python-libxml2 python-libxslt1 python-imaging python-gdata python-ldap python-reportlab python-pyparsing python-simplejson python-pydot python-webdav graphviz python-werkzeug python-matplotlib python-vatnumber python-numpy python-pychart python-vobject python-zsi python-xlwt python-hippocanvas python-profiler python-dev python-setuptools postgresql postgresql-client-common python-yaml python-mako gcc mc python-babel python-feedparser python-reportlab-accel python-zsi python-openssl python-jinja2 python-unittest2 python-mock  python-docutils lptools make python-psutil python-paramiko poppler-utils python-pdftools antiword python-jinja2 python-requests git-core sudo python-decorator python-pypdf python-passlib xsltproc xmlstarlet python-soappy python-qrencode curl npm && curl -sL https://deb.nodesource.com/setup | bash - && apt-get -y install nodejs && npm install -g npm && npm install -g less less-plugin-clean-css

http://misnotasdelinux.blogspot.mx/2015/10/instalar-odoo-9-en-debian-8.html

1- install node-less: apt-get install node-less

2- Restart postgresql service: sudo service postgresql restart

3- Restart the sever.

Try this

sudo apt-get install lxc

Check out http://askubuntu.com/questions/63099/command-not-found-when-running-lessc-from-bash - it should do the job for you.