I was logged into npm (via npm login) and went to do a global install of one of my private packages (npm i -g), only to be confronted with an E404 NOT FOUND error.

After some initial confusion, I realized it was because my setup requires using sudo for global npm installs: sudo makes you take on the role of the root user, and so it doesn't have access to your regular user's npm credentials!

There are two easy solutions to this:

Log into npm with sudo

The easiest thing to do is to also log into your npm account with root, so that when you use sudo the command will have access to your npm credentials.

sudo npm login

Stop having to use sudo for global installs

It's probably better to not have to use sudo at all for your global installs.

To address that, you need npm to use a directory that your regular user has permissions to access. Fortunately, npm makes this easy to do. A handful of people have put together a super simple guide for this. In short:

First create a new directory with your regular user and tell npm to use it:

  mkdir "${HOME}/.npm-packages"
  npm config set prefix "${HOME}/.npm-packages"

Then give npm a little more help finding binaries and such by updating your .bashrc file:

  # @file ~/.bashrc
  NPM_PACKAGES="${HOME}/.npm-packages"

  export PATH="$PATH:$NPM_PACKAGES/bin"

  # Preserve MANPATH if you already defined it somewhere in your config.
  # Otherwise, fall back to `manpath` so we can inherit from `/etc/manpath`.
  export MANPATH="${MANPATH-$(manpath)}:$NPM_PACKAGES/share/man"

The guide has more details to help out with other use cases.