How to suppress installing rdoc/ri docs when running gem install

• Posted 26 November 2018
• Tagged with docker, ruby

If you try to run gem install in a Docker container which only contains a Ruby package (and no rdoc or ri), you get an error:

Step 3/5 : RUN gem install rack
 ---> Running in 8ee24453f7a9
ERROR:  While executing gem ... (Gem::DocumentError)
    RDoc is not installed: cannot load such file -- rdoc/rdoc

If you add the following line to your .gemrc, it skips trying to install the docs.

install: --no-rdoc --no-ri

Handy if you’re in a Docker image that will never run interactively!