Install Prerequisites

yum install -y curl gcc-c++ patch readline readline-devel zlib zlib-devel libyaml-devel libffi-devel openssl-devel make cmake bzip2 autoconf automake libtool bison libssh2-devel libicu-devel

Install RVM

curl -L get.rvm.io | bash -s stable

Setup RVM, install Ruby 2.6.1 and set to default.

source /etc/profile.d/rvm.sh 
rvm install 2.6.1 
rvm use --default 2.6.1

You may need to add root or the user your using to the rvm group

sudo usermod -G rvm username

Pulled some of the info from here https://github.com/ytti/oxidized#installing-ruby-212-using-rvm