erro @node não pode encontrar o módulo já instalado

[root@zexu websocket_start]# npm ls -g installed
npm WARN ls doesn't take positional args. Try the 'search' command
npm WARN [email protected] package.json: bugs['web'] should probably be bugs['url']
/usr/lib
├─┬ [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ ├── [email protected] 
│ └── [email protected] 
└── [email protected] 
[root@zexu websocket_start]# npm ls  installed
npm WARN ls doesn't take positional args. Try the 'search' command
/home/qonco/workspace/JS/websocket_start
(empty)
[root@zexu websocket_start]# node
> require("websocket-server");
Error: Cannot find module 'websocket-server'
    at Function._resolveFilename (module.js:332:11)
    at Function._load (module.js:279:25)
    at Module.require (module.js:354:17)
    at require (module.js:370:17)
    at repl:1:1
    at REPLServer.eval (repl.js:80:21)
    at repl.js:190:20
    at REPLServer.eval (repl.js:87:5)
    at Interface. (repl.js:182:12)
    at Interface.emit (events.js:67:17)
> 

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