$ bundle config NAME [VALUE]     # Retrieve or set a configuration value
$ bundle config set NAME VALUE   # Sets the given value for the given key
$ bundle config list             # List out all configured settings

Make sure to configure Bundle first before installing.

This is common:

$ bundle config set --local path vendor/bundle

That will create - .bundle/config file.

Make sure to ignore the file, as it is environment-specific:

  • .gitignore 
      .bundle

In the case of using the frozen or deploy flags, you’ll get values added to the config too.

Clean mode

clean - Whether Bundler should run bundle clean automatically after bundle install.

Deploy mode

Disallow changes to the Gemfile.lock file.

Use the deploy option when configuring. TBC is it true or True?

$ bundle config set deployment true

deployment - Disallow changes to the Gemfile. When the Gemfile is changed and the lockfile has not been updated, running Bundler commands will be blocked.

Previously, you would set this option, which is now deprecated.

$ bundle install --deployment

From the help:

This option is deprecated in favor of the deployment setting.

Notes from docs

The --deployment flag requires an up-to-date Gemfile.lock to ensure that the testing you have done (in development and staging) actually reflects the code you put into production.

You can run bundle check before deploying your application to make sure that your Gemfile.lock is up-to-date.

Note that it will always be up-to-date if you have run bundle install, successfully booted your application (or run your tests) since the last time you changed your Gemfile.