接着上一篇文章，redis集群配置：
https://blog.csdn.net/u010533511/article/details/89388547
Redis 3.0以上的集群方式是通过Redis安装目录下的redis-trib.rb脚本搭建。
这个脚本是用Ruby编写的，所以要先安装Ruby环境
yum安装ruby和依赖的包。
# yum -y install ruby ruby-devel rubygems
一般来说，这一步是能正常完成的。
使用gem这个命令来安装redis接口
gem install redis
ERROR: Error installing redis:
redis requires Ruby version >= 2.2.2.
CentOS7 yum库中ruby的版本支持到 2.0.0，可gem 安装redis需要最低是2.2.2，采用rvm来更新ruby
安装RVM（具体RVM安装命令地址：http://rvm.io/）
[root@localhost /]# gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB
[root@localhost /]# curl -sSL https://get.rvm.io | bash -s stable
[root@localhost /]# find / -name rvm -print
/usr/local/rvm
/usr/local/rvm/src/rvm
/usr/local/rvm/src/rvm/bin/rvm
/usr/local/rvm/src/rvm/lib/rvm
/usr/local/rvm/src/rvm/scripts/rvm
/usr/local/rvm/bin/rvm
/usr/local/rvm/lib/rvm
/usr/local/rvm/scripts/rvm
立即生效
[root@localhost /]# source /usr/local/rvm/scripts/rvm
查看已知ruby版本
# rvm list known
[ruby-]1.8.6[-p420]
[ruby-]1.8.7[-head] # security released on head
[ruby-]1.9.1[-p431]
[ruby-]1.9.2[-p330]
[ruby-]1.9.3[-p551]
[ruby-]2.0.0[-p648]
[ruby-]2.1[.10]
[ruby-]2.2[.10]
[ruby-]2.3[.7]
[ruby-]2.4[.4]
[ruby-]2.5[.1]
[ruby-]2.6[.0-preview2]
......
安装一个ruby版本：
#rvm install 2.5.1
Searching for binary rubies, this might take some time.
Found remote file https://rvm_io.global.ssl.fastly.net/binaries/centos/7/x86_64/ruby-2.5.1.tar.bz2
Checking requirements for centos.
Requirements installation successful.
ruby-2.5.1 - #configure
ruby-2.5.1 - #download
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 14.1M 100 14.1M 0 0 97k 0 0:02:27 0:02:27 --:--:-- 159k
No checksum for downloaded archive, recording checksum in user configuration.
ruby-2.5.1 - #validate archive
ruby-2.5.1 - #extract
ruby-2.5.1 - #validate binary
ruby-2.5.1 - #setup
ruby-2.5.1 - #gemset created /usr/local/rvm/gems/ruby-2.5.1@global
ruby-2.5.1 - #importing gemset /usr/local/rvm/gemsets/global.gems..............................
ruby-2.5.1 - #generating global wrappers........
ruby-2.5.1 - #gemset created /usr/local/rvm/gems/ruby-2.5.1
ruby-2.5.1 - #importing gemsetfile /usr/local/rvm/gemsets/default.gems evaluated to empty gem list
ruby-2.5.1 - #generating default wrappers........
使用某个Ruby版本：
# rvm use 2.5.1
Using /usr/local/rvm/gems/ruby-2.5.1
设置默认版本：
#rvm use 2.5.1 --default
Using /usr/local/rvm/gems/ruby-2.5.1
卸载某个已知ruby版本：
#rvm remove 2.5.1
查看ruby版本：
[root@localhost redis]# ruby -v
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]
至此，ruby版本已经升级至2.5.1，可以使用gem安装redis了
# gem install redis
Fetching: redis-4.0.1.gem (100%)
Successfully installed redis-4.0.1
Parsing documentation for redis-4.0.1
Installing ri documentation for redis-4.0.1
Done installing documentation for redis after 3 seconds
1 gem installed
安装redis成功
# yum install -y rubygems
Loaded plugins: fastestmirror, security
Setting up Install Process
Loading mirror speeds from cached hostfile
base | 3.7 kB 00:00
didi_jenkins_enable | 1.5 kB 00:00
didi_op_toa_enable | 1.5 kB 00:00
didi_txjenkins_enable | 1.5 kB 00:00
didi_update | 1.5 kB 00:00
epel | 4.3 kB 00:00
extras | 3.4 kB 00:00
tmprepo | 1.5 kB 00:00
updates | 3.4 kB 00:00
Package rubygems-1.3.7-5.el6.noarch already installed and latest version
Nothing to do
安装rubygems，成功！
至此，我们的Ruby和运行redis-trib.rb需要的环境安装完成了。