ubuntu 11.10安装 rvm
从 https://rvm.io/rvm/install/#explained 查看安装：

song@song-laptop:~$ curl https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer | bash -s stable  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current                                 Dload  Upload   Total   Spent    Left  Speed100  8844  100  8844    0     0   1318      0  0:00:06  0:00:06 --:--:--  1491mkdir: cannot create directory `/usr/share/ruby-rvm': Permission denied

结果报错：Permission denied
解决方法执行：sudo apt-get --purge remove ruby-rvm
参数--purge的意思是- Remove packages and config files
然后再次按照教程安装
curl -L get.rvm.io | bash -s stable