安装 tj 写的版本管理工具 n 模块后,出现如下问题.原来用 nvm 管理没问题,但是现在用也会出错,请问是什么原因呢?非常感谢!

[we]

``` bash
➜ ~ npm install -g n
/home/joes/.nvm/v0.10.38/bin/n -> /home/joes/.nvm/v0.10.38/lib/node_modules/n/bin/n
n@2.0.2 /home/joes/.nvm/v0.10.38/lib/node_modules/n
➜ ~ n
mkdir: cannot create directory ‘/usr/local/n/versions ’: Permission denied
mkdir: cannot create directory ‘/usr/local/n/versions ’: Permission denied
find: '/usr/local/n/versions': No such file or directory

Error: no installed version
```
```bash
➜ ~ nvm

module.js:340
throw err;
^
Error: Cannot find module './nvm-help'
at Function.Module._resolveFilename (module.js:338:15)
at Function.Module._load (module.js:280:25)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at Object.<anonymous> (/home/joes/.nvm/v0.10.38/lib/node_modules/nvm/bin/nvm:24:3)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)
```