在执行gem install redis时，报错：

gem install redis
    ERROR:  Error installing redis:
            redis requires Ruby version >= 2.2.2.

这句话的意思是，安装redis需要ruby版本最低是2.2.2，而centos yum库中ruby版本支持到2.0.0。所以，无法满足需求。


1、安装RVM

gpg2 --keyserver hkp://keys.gnupg.net --recv-keys D39DC0E3
    curl -L get.rvm.io | bash -s stable
    find / -name rvm -print

2、查看rvm库中已知的ruby版本

rvm list known

MRI Rubies


[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[.6]


[ruby-]2.3[.3]


[ruby-]2.4[.0]


ruby-head


3、安装一个ruby版本

rvm install 2.3.3

No checksum for downloaded archive, recording checksum in user configuration.


ruby-2.3.3 - #extracting rubygems-2.6.12….


ruby-2.3.3 - #removing old rubygems………


ruby-2.3.3 - #installing rubygems-2.6.12…………………….


ruby-2.3.3 - #gemset created /usr/local/rvm/gems/ruby-2.3.3@global


ruby-2.3.3 - #importing gemset /usr/local/rvm/gemsets/global.gems…………..|


ruby-2.3.3 - #generating global wrappers……..


ruby-2.3.3 - #gemset created /usr/local/rvm/gems/ruby-2.3.3


ruby-2.3.3 - #importing gemsetfile /usr/local/rvm/gemsets/default.gems evaluated to empty gem list


ruby-2.3.3 - #generating default wrappers……..


ruby-2.3.3 - #adjusting #shebangs for (gem irb erb ri rdoc testrb rake).


Install of ruby-2.3.3 - #complete


Ruby was built without documentation, to build it run: rvm docs generate-ri



4、使用一个ruby版本


rvm use 2.3.3

Using /usr/local/rvm/gems/ruby-2.3.3


5、设置默认版本

rvm use 2.3.3 --default

Using /usr/local/rvm/gems/ruby-2.3.3


6、卸载一个已知版本

rvm remove 2.0.0

7、查看ruby版本


ruby --version

ruby 2.3.3p222 (2016-11-21 revision 56859) [x86_64-linux]

8、安装redis

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 0 seconds


1 gem installed


完成！！！