安装ruby

$ ruby -v
ruby 1.9.3p484 (2013-11-22 revision 43786) [x86_64-linux]

$ gem -v
1.8.23

参考https://launchpad.net/~brightBox/+archive/ubuntu/ruby-ng

添加ruby的ppa源

sudo add-apt-repository ppa:brightBox/ruby-ng

 Next generation Ubuntu packages for Ruby 2.3,2.2,2.1,2.0 1.9.3 and 1.8 EE.

See https://www.brightBox.com/docs/ruby/ubuntu/ for more details.

This PPA no longer includes Phusion Passenger packages,and Nginx packages with Passenger support. See https://launchpad.net/~brightBox/+archive/ubuntu/passenger-legacy

Discussion list here: https://groups.google.com/forum/#!forum/brightBox-ruby-ubuntu-packaging

https://www.brightBox.com
 More info: https://launchpad.net/~brightBox/+archive/ubuntu/ruby-ng
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keyring `/tmp/tmp6rrmbv29/secring.gpg' created
gpg: keyring `/tmp/tmp6rrmbv29/pubring.gpg' created
gpg: requesting key C3173AA6 from hkp server keyserver.ubuntu.com
gpg: /tmp/tmp6rrmbv29/trustdb.gpg: trustdb created
gpg: key C3173AA6: public key "Launchpad PPA for BrightBox" imported
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
OK

更新

sudo apt-get update

sudo apt-get install ruby2.3
sudo apt-get install ruby2.3-dev

$ ruby -v 
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux-gnu]

$ gem -v
2.5.1

sudo gem update --system -V

sudo gem sources --add https://gems.ruby-china.org/ --remove https://rubygems.org/

sudo gem update -V