Why do i have to call npm link as administrator? - node.js

Question

I installed some nodejs packages globally via
sudo npm install gulp -g
Now I (or another developer on the same machine) wants to use it in a project with
me#host:/my/project$ npm link gulp
It fails with
unbuild gulp#3.8.11
npm ERR! Error: EPERM, chmod '/my/projectnode_modules/gulp/bin/gulp.js'
npm ERR! { [Error: EPERM, chmod '/my/projectnode_modules/gulp/bin/gulp.js']
npm ERR! errno: 50,
npm ERR! code: 'EPERM',
npm ERR! path: '/my/projectnode_modules/gulp/bin/gulp.js' }
npm ERR!
npm ERR! Please try running this command again as root/Administrator.
npm ERR! System Linux 3.2.0-4-amd64
npm ERR! command "/usr/bin/nodejs" "/usr/bin/npm" "link" "gulp"
npm ERR! cwd /raid5/workspaces/jgr/aktivglueck-laravel
npm ERR! node -v v0.10.29
npm ERR! npm -v 1.4.21
npm ERR! path /my/projectnode_modules/gulp/bin/gulp.js
npm ERR! code EPERM
npm ERR! errno 50
npm ERR! stack Error: EPERM, chmod '/my/projectnode_modules/gulp/bin/gulp.js'
npm ERR!
npm ERR! Additional logging details can be found in:
npm ERR! /my/projectnpm-debug.log
npm ERR! not ok code 0
With
sudo npm link gulp
everything works fine.
What I want to know is: Why does npm link need admin permissions? In my understanding I am creating a link inside my project folder where I have full permissions - so what does it do on the global system?

Answer 1

I believe npm link creates a symlink to the current directory in wherever your globally installed node packages are. See here.
If you don't have write rights to that path (you can check with npm config get prefix) you'll get the error you see there.
To avoid having to sudo global installs/links, you could change the ownership/rights of that directory.