Anda tidak memiliki izin menulis untuk direktori /var/lib/gems/2.3.0

Saya telah menginstal ruby ​​di ubuntu 16.04 saya. $which ruby /usr/bin/ruby $ruby -v ruby 2.3.0p0 (2015-12-25) [x86_64-linux-gnu] $gem install bundler ERROR: While executing gem ... (Gem::FilePermissionError) You don't have write permissions for the /var/lib/gems/2.3.0...