Now that glyphicons have been phased out in Bootstrap 4, I needed an alternative and found opticons.
To install it:
First install Node Package Manager (npm):
curl -sL https://deb.nodesource.com/setup_6.x | sudo bash - apt-get install nodejs wget https://github.com/primer/octicons/archive/v5.0.1.zip unzip v5.0.1.zip cd octicons-5.0.1/
Now we need to edit the json to prevent npm from aborting saying that opticons cant be installed as a dependency of itself.
Change the line:
npm install octicons –save
npm run build
Now the required files are available at ./build/