在使用命令npm install -g yarn 安装yarn时出现了下面的报错。

npm ERR! errno -13
npm ERR! Error: EACCES: permission denied, mkdir '/usr/local/lib/node_modules/yarn'
npm ERR!  [Error: EACCES: permission denied, mkdir '/usr/local/lib/node_modules/yarn'] {
npm ERR!   errno: -13,
npm ERR!   code: 'EACCES',
npm ERR!   syscall: 'mkdir',
npm ERR!   path: '/usr/local/lib/node_modules/yarn'
npm ERR! }
npm ERR! 
npm ERR! The operation was rejected by your operating system.
npm ERR! It is likely you do not have the permissions to access this file as the current user
npm ERR! 
npm ERR! If you believe this might be a permissions issue, please double-check the
npm ERR! permissions of the file and its containing directories, or try running
npm ERR! the command again as root/Administrator.

记得前几天也遇到过，解决方法如下：

将命令npm install -g yarn 

换成sudo npm install -g yarn

即可