Brew Error: /usr/local must be writable!

Everyone loves Brew, except when Brew doesn’t Brew.

Error: /usr/local must be writable!

This is caused by ownership and permission issues of the /usr/local folder and the currently controlled account.

You can sudo the update however Brew may cry and refuse without changing the ownership of the executable to root.

For a quick fix, run the following:

sudo chgrp -R admin /usr/local
sudo chmod -R g+w /usr/local
brew update

Ta da.

Sometimes things go wrong inside the world of /usr/local and certain items lose their ability to be written to by all admin users. These commands effectively remind everyone who’s boss.

Notes of Nuisance