root@iZ2zecacx22uir8ou95g65Z:~# npm -v

报错

internal/modules/cjs/loader.js:968
throw err;
^

Error: Cannot find module ‘…/lib/utils/unsupported.js’
Require stack:

• /opt/node/lib/node_modules/npm/bin/npm-cli.js
  at Function.Module._resolveFilename (internal/modules/cjs/loader.js:965:15)
  at Function.Module._load (internal/modules/cjs/loader.js:841:27)
  at Module.require (internal/modules/cjs/loader.js:1025:19)
  at require (internal/modules/cjs/helpers.js:72:18)
  at /opt/node/lib/node_modules/npm/bin/npm-cli.js:19:21
  at Object. (/opt/node/lib/node_modules/npm/bin/npm-cli.js:155:3)
  at Module._compile (internal/modules/cjs/loader.js:1137:30)
  at Object.Module._extensions…js (internal/modules/cjs/loader.js:1157:10)
  at Module.load (internal/modules/cjs/loader.js:985:32)
  at Function.Module._load (internal/modules/cjs/loader.js:878:14) {
  code: ‘MODULE_NOT_FOUND’,
  requireStack: [ ‘/opt/node/lib/node_modules/npm/bin/npm-cli.js’ ]
  }

解决

试尽各种办法，最后还是手动卸载了再重装了npm
1、sudo npm uninstall npm -g
如果步骤1卸不掉npm了（我就是这种情况）
2、进到npm的安装目录 /opt/node/lib/node_modules/npm （这是我的地址）
sudo make uninstall
3、手动重装npm
curl -L https://npmjs.com/install.sh | sh

控制版本

$ npm install -g n