How do I downgrade Ruby to 1.8.7 on RightImages 13.2 and 13.3?

Background

With the v13.2 ServerTemplate release, all images were upgraded to version 1.9.3. However, users may require an older version. The user must downgrade ruby to version 1.8.7 manually.

Answer

Execute the following on the command line of a v13.2 Linux RightImage instance logged in as 'root':

For CentOS and RedHat:

yum erase ruby ruby-libs
yum install ruby-1.8.*
yum install rubygems

For Ubuntu:

apt-get install ruby1.8 rubygems (may already be installed)
update-alternatives --set ruby "/usr/bin/ruby1.8"
update-alternatives --set gem "/usr/bin/gem1.8"