odoo9 的安装需要 nodejs 的 lessc 命令。 需要先安装nodejs 后，使用nmp（nodejs的一个包管理工具） 安装lessc等功能。
window
1:安装nodejs。 安装后需要重启
2：npm install -g less less-plugin-clean-css
如何安装有错误，找不到package.json文件 ，则先cd到 C:Program Files odejs ode_modulesamdefine（package.json的目录）
on Linux, use your distribution’s package manager to install nodejs and npm.
Warning
In debian wheezy and Ubuntu 13.10 and before you need to install nodejs manually:
$ wget -qO- https://deb.nodesource.com/setup | bash -
$ apt-get install -y nodejs
In later debian (>jessie) and ubuntu (>14.04) you may need to add a symlink as npm packages call node but debian calls the binary nodejs
$ apt-get install -y npm
$ sudo ln -s /usr/bin/nodejs /usr/bin/node
$ sudo npm install -g less less-plugin-clean-css
$ sudo npm install -g less less-plugin-clean-css
on OS X, install nodejs via your preferred package manager (homebrew, macports) then install less and less-plugin-clean-css:
$ sudo npm install -g less less-plugin-clean-css
on Windows, install nodejs, reboot (to update the PATH) and install less and less-plugin-clean-css:
C:> npm install -g less less-plugin-clean-css
--------cetos6.5-------
yum install -y nodejs
yum install -y npm
ln -s /usr/bin/nodejs /usr/bin/node
npm install -g less less-plugin-clean-css
reboot