How To: Mass password reset and email notification

# path: lib/tasks/devise.rake

namespace :devise do
  desc "Send password reset instructions and link but does not actually reset passwords"
  task mass_password_reset: :environment do
    User.all.each do |user|
      # This only sends the password reset instructions, the
      # password is not changed. (Recipient has to click link
      # in email and follow instructions to actually change
      # the password).
      user.send_reset_password_instructions
    end
  end
end