准备做redis-cluster，需要ruby2.2环境

开整
环境：Centos7.2最小安装
yum源：阿里的base和epel源

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Install Dependencies
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yum -y groupinstall "Development Tools"
yum -y install gdbm-devel libdb4-devel libffi-devel libyaml libyaml-devel ncurses-devel openssl-devel readline-devel tcl-devel

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Download and Build Ruby from Source
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mkdir -p rpmbuild/{BUILD,BUILDROOT,RPMS,SOURCES,SPECS,SRPMS}

wget http://cache.ruby-lang.org/pub/ruby/2.2/ruby-2.2.3.tar.gz -P rpmbuild/SOURCES

wget https://raw.githubusercontent.com/tjinjin/automate-ruby-rpm/master/ruby22x.spec -P rpmbuild/SPECS

rpmbuild -bb rpmbuild/SPECS/ruby22x.spec

yum -y localinstall rpmbuild/RPMS/x86_64/ruby-2.2.3-1.el7.centos.x86_64.rpm

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Test the Install
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ruby -v
gem -v

网上好多都是编译安装，坑太多，需要改ssl相关的代码

这个方法比较适合我这样的小白