$ sudo yum install git\
tree\
gcc gcc-c++ make\
libffi libffi-devel\
zlib zlib-devel\
openssl openssl-devel\
httpd-tools\
libxml2 libxml2-devel\
libxslt libxslt-devel\
readline-devel
$ git clone https://github.com/sstephenson/rbenv.git ~/.rbenv
$ git clone https://github.com/sstephenson/ruby-build.git ~/.rbenv/plugins/ruby-build
$ echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile
$ echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
$ source .bash_profile
$ rbenv --version
=> rbenv 0.4.0-133-g98953c2
$ rbenv install --list
=> Available versions:
1.8.6-p383
...（略
$ rbenv install 2.2.0
=> Downloading ruby-2.2.0.tar.gz...
-> http://dqw8nmjcqpjn7.cloudfront.net/7671e394abfb5d262fbcd3b27a71bf78737c7e9347fa21c39e58b0bb9c4840fc
Installing ruby-2.2.0...
Installed ruby-2.2.0 to /home/ec2-user/.rbenv/versions/2.2.0
$ rbenv global 2.2.0
$ ruby -v
=> ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-linux]
$ gem i bundler