The command bundle install tells your ruby / rails application to read the Gemfile and install or update the components in Gemfile. The elixir equivalent to Gemfile is mix.exs and the command to update it is:

mix deps.get

A sample mix.exs file looks quite different from Gemfile. Here's an example of just the defp deps method where the equivalent to gems are listed:

defp deps do
  [{:mariaex, ">= 0.0.0"},
   {:ecto, "~> 2.0"},
   {:aws, "~> 0.2.0"}]