I got the error message “Error: Unknown command: cask” while trying to install multipass using brew cask command. This is as shared in code section:

$ brew cask install multipass
Error: Unknown command: cask

The reason you’ll get this error is that cask is no longer a brew command. Whenever you want to install a Cask, you will run the command:

brew install <package>
# OR
brew install --cask <package>

Instead of brew cask install. So let’s rerun the installation and see the results:

$ brew  install --cask multipass
==> Downloading https://github.com/CanonicalLtd/multipass/releases/download/v1.6
==> Downloading from https://github-releases.githubusercontent.com/114128199/4dd
######################################################################## 100.0%
==> Installing Cask multipass
==> Running installer for multipass; your password may be necessary.
Package installers may write to any location; options such as `--appdir` are ignored.
Password:
installer: Package name is multipass
installer: Installing at base path /
installer: The install was successful.
🍺  multipass was successfully installed!

Reading brew help pages is also helpful when you encounter any error while using the command. Here are common ways of getting help:

brew help
man brew
brew help <command>

See brew common usage examples:

$ brew help
Example usage:
  brew search TEXT|/REGEX/
  brew info [FORMULA|CASK...]
  brew install FORMULA|CASK...
  brew update
  brew upgrade [FORMULA|CASK...]
  brew uninstall FORMULA|CASK...
  brew list [FORMULA|CASK...]

Troubleshooting:
  brew config
  brew doctor
  brew install --verbose --debug FORMULA|CASK

Contributing:
  brew create URL [--no-fetch]
  brew edit [FORMULA|CASK...]

Further help:
  brew commands
  brew help [COMMAND]
  man brew
  https://docs.brew.sh

I hope this guide was of importance to you in bypassing the error stated while trying to install a package using brew package manager on macOS. The error “error: unknown command: cask” should be no issue from now onwards.

More guides on macOS are shared in the links below:

• How To Install GNS3 on macOS Big Sur
• How To Fetch CPU Information on Linux|macOS using cpufetch

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