LESS
About Recess
Recess is a tool used to compile and compress LESS into CSS under *nix based systems.
Installing Recess under Ubuntu
The following commands should be run to install Recess
sudo apt-get install npm node npm install recess -g
Using Recess
To compile to LESS for the boostrap them use these commands, from the root of your moodle code directory
cd theme/boostrap/less/ recess --compile --compress moodle.less ../style/generated.css
This will compile and compress the moodle.less file (and all the LESS and CSS files it imports) into a single file, generated.css, and store it in the style folder of the bootstrap theme.
NOTE: if you are getting empty generated.css files, this is being caused by a parsing error in your LESS code. You will need to examine what you have altered or written to make sure it is complete and the syntax is correct.