homebrew update on Mac: /usr/local not writable

Sometimes the most obvious solution isn’t so obvious

On my work MacBookPro laptop I issued the following Terminal Command:

brew update

it promptly came back:

 Error: /usr/local must be writable!


Doing a little web Googling and Face-2-Face conversing here in shop I learned the solution:

  • change ownership the to your current user :> whoami
sudo chown -R $(whoami) /usr/local
  • When this is successful re-execute brew update
brew update
  • When complete revert ownership of /usr/local back to root
sudo chown -R root /user/local


BAM – Homebrew update is happy, obviously 🙂

Some material for this post leveraged from github forum:  https://github.com/Homebrew/brew/issues/476