How to fix 'npm install' errors on OS X

September 14, 2014

TL;DR

sudo chown -R $USER /usr/local
sudo chown -R $USER ~/.npm

I’ve had this problem for a while: fresh nodejs and npm installation, I try to run npm install or npm install -g and get all kind of errors.

Errors when running `npm install` without the `-g` flag

When running without the -g flag, I usually get, among the others: Error: Attempt to unlock XXX, which hasn't been locked.

Errors when running `npm install -g`

When you run npm install with the -g option, you want to be able to run a specific executable (a .js file) from outside any project folder with a node_modules directory.
In this case, you usually get another access error:

npm ERR! Error: EACCES, mkdir '/usr/local/lib/node_modules/...'
npm ERR!  { [Error: EACCES, mkdir '/usr/local/lib/node_modules/...']
npm ERR!   errno: 3,
npm ERR!   code: 'EACCES',
…
npm ERR! Please try running this command again as root/Administrator.

Understand what happens under the hood

Let’s first have a look at what happens when you run these commands.

What happens when you run `npm install` (without the `-g` flag)?

Example for the traceur compiler:

$ npm install traceur
...
[email protected] node_modules/traceur

npm creates a node_modules folder (if it does not exists) and install the package under that folder

As you can see, it is installed under node_modules/traceur.

What happens when you run `npm install -g`?

Example for the traceur compiler:

$ npm install traceur -g
...
/usr/local/bin/traceur -> /usr/local/lib/node_modules/traceur/traceur

npm installs the package under /usr/local/lib/node_modules
a symbolic link is created from that folder to usr/local/bin/

The easy and bad solution

In both cases, running sudo npm install, immediately fixes the problem.

The right solution

In no case you should run npm with sudo.
You can read the Intro to npm by Isaac Schlueter for a valid reason.

Packages can run arbitrary scripts, which makes sudoing a package manager command as safe as a chainsaw haircut

So, the short answer is: to avoid security issues.

The source of the problem

What is happening when you get the error is that the user you are logged in with does not have the rights to run that command.
This is usually because npm was installed by root and so you are not the owner of that executable file.

Fix your `/usr/local` folder

If you run which npm on your Mac, you should get:

$ which npm
/usr/local/bin/npm

The /usr/local folder is the folder where the user install his own stuff, so it belongs to the user.
To fix the problem: sudo chown -R $USER /usr/local

Your npm will be back to you now.

Fix your `~/.npm` folder

Before considering it done, have a look at your home folder: you have a .npm folder in it.

You have to make sure that the whole folder belongs to your user and to do that, issue: sudo chown -R $USER ~/.npm

The .npm folder is now yours and you’ll be able to run npm install and npm install -g without sudo: enjoy.

Recap

When you get weird errors using npm install and npm install -g that are solved using these commands with sudo, have a look at the owner of your /usr/local and ~/.npm folders: changing it to your user will solve the problems.

Sources:

TL;DR

Errors when running npm install without the -g flag

Errors when running npm install -g