Can I change Homebrew's prefix?

Question

Somehow, my Homebrew install has a prefix of ~/.rvm. I'd like to set it to the default of /usr/local.

Is this possible?

Answer 1

For the benefit of anyone who's had to do a manual install of Homebrew.

Taking a look at the actual brew file is the line:

HOMEBREW_PREFIX="${HOMEBREW_BREW_FILE%/*/*}"

It turns out it gets the prefix automatically from the parent directory of the install location, unless;

# Try to find a /usr/local HOMEBREW_PREFIX where possible (for bottles)
if [[ -L "/usr/local/bin/brew" ]]
then
  USR_LOCAL_BREW_FILE_DIRECTORY="$(symlink_target_directory "/usr/local/bin/brew" "/usr/local/bin")"
  USR_LOCAL_HOMEBREW_REPOSITORY="${USR_LOCAL_BREW_FILE_DIRECTORY%/*}"
  if [[ "$HOMEBREW_REPOSITORY" = "$USR_LOCAL_HOMEBREW_REPOSITORY" ]]
  then
    HOMEBREW_PREFIX="/usr/local"
  fi
fi

This'll grab the prefix value from the parent directory of any symlink to the brew executable so long as the Homebrew install directory is down stream from that directory (like /usr/local/Homebrew)

If you've manually installed directly into the usr/local/ directory, you'll still want to go and put a symlink in the usr/local/bin folder to your Homebrew/bin/brew executable to get the correct prefix path. That'll also avoid you needing to add the Homebrew/bin folder directly to your $PATH as well.

Answer 2

Some of Homebrew's bottles (binary packages) can only be used with the default prefix (/usr/local) like e.g. rust. But if you still want to install it with a different prefix, then use:

arch -arm64 brew install rust

If you want to know, which prefix you already using:

brew config | grep HOMEBREW_PREFIX

In my case it is HOMEBREW_PREFIX: /opt/homebrew