Mac Big sur Gem Ignoring because its extensions are not built problems try gem pristine --all tip: permission issues check ruby which ruby then brew link --overwrite ruby && source ~/.bash_profile or (OnMy ZSH commond tool) brew link --overwrite ruby && source ~/.zshrc then gem pristine --all Mac Big sur Brew update Problem try brew update tip git -C "/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core" fetch --unshallow cd /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core git fetch git fetch --unshallow tip git -C "/usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask" fetch --unshallow cd /usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask git fetch git fetch --unshallow then brew update