在安装appium 或者升级npm的过程中会遇到这个问题。出错时的代码提示如下：
npm ERR! path /usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri
npm ERR! code EACCES
npm ERR! errno -13
npm ERR! syscall access
npm ERR! Error: EACCES: permission denied, access '/usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri'
npm ERR! { Error: EACCES: permission denied, access '/usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri'
npm ERR! stack: 'Error: EACCES: permission denied, access \'/usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri\'',
npm ERR! errno: -13,
npm ERR! code: 'EACCES',
npm ERR! syscall: 'access',
npm ERR! path: '/usr/local/lib/node_modules/npm/node_modules/cacache/node_modules/ssri' }
npm ERR!
npm ERR! Please try running this command again as root/Administrator. npm ERR! A complete log of this run can be found in
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解决方案：
sudo npm i -g npm