您需要编辑$PATH环境变量.

例如，在您的.bashrc中:

export PATH=$PATH:/var/lib/gems/1.8/bin

或者，您可以在.bashrc中使用别名:

Alternatively, you can use an alias, in your .bashrc:

alias rails=/var/lib/gems/1.8/bin/rails

或者您甚至可以将rails二进制文件(或符号链接)放入$PATH中列出的目录之一.要查看这些目录，请键入echo $PATH.

Or you could even put the rails binary (or a symlink) to one of the directories listed in your $PATH. To see those directories, type echo $PATH.