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A cache and private gem server


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What is Gemstash?

Gemstash is both a cache for remote servers such as, and a private gem source.

If you are using bundler across many machines that have access to a server within your control, you might want to use Gemstash.

If you produce gems that you don’t want everyone in the world to have access to, you might want to use Gemstash.

If you frequently bundle the same set of gems across multiple projects, you might want to use Gemstash.

Are you only using gems from, and don’t bundle the same gems frequently? Well, maybe you don’t need Gemstash… yet.

Gemstash is maintained by Ruby Central, a non-profit committed to supporting the critical Ruby infrastructure you rely on. Contribute today as an individual, or even better, as a company, and ensure that Bundler, RubyGems, Gemstash, and other shared tooling is around for years to come.

Quickstart Guide


Gemstash is designed to be quick and painless to get set up. By the end of this Quickstart Guide, you will be able to bundle stashed gems from public sources against a Gemstash server running on your machine.

Install Gemstash to get started:

$ gem install gemstash

After it is installed, starting Gemstash requires no additional steps. Simply start the Gemstash server with the gemstash command:

$ gemstash start

You may have noticed that the command finished quickly. This is because Gemstash will run the server in the background by default. The server runs on port 9292.


With the server running, you can bundle against it. Tell Bundler that you want to use Gemstash to find gems from

$ bundle config mirror. http://localhost:9292

Now you can create a Gemfile and install gems through Gemstash:

# ./Gemfile
source ""
gem "rubywarrior"

The gems you include should be gems you don’t yet have installed, otherwise Gemstash will have nothing to stash. Now bundle:

$ bundle install --path .bundle

Your Gemstash server has fetched the gems from and cached them for you! To prove this, you can disable your Internet connection and try again. Gem files (*.gem) are cached indefinitely. Gem dependencies metadata are cached for 30 minutes, so if you bundle again before that, you can successfully bundle without an Internet connection:

$ # Disable your Internet first!
$ rm -rf Gemfile.lock .bundle
$ bundle

Falling back to

If you want to make sure that your bundling from still works as expected when the Gemstash server is not running, you can easily configure Bundler to fallback to

$ bundle config mirror. true

You can also configure this fallback as a number of seconds in case the Gemstash server is simply unresponsive. This example uses a 3 second timeout:

$ bundle config mirror. 3

Stopping the Server

Once you’ve finish using your Gemstash server, you can stop it just as easily as you started it:

$ gemstash stop

You’ll also want to tell Bundler that it can go back to getting gems from directly, instead of going through Gemstash:

$ bundle config --delete mirror.

Under the Hood

You might wonder where the gems are stored. After running the commands above, you will find a new directory at ~/.gemstash. This directory holds all the cached and private gems. It also has a server log, the database, and configuration for Gemstash. If you prefer, you can point to a different directory.

Gemstash uses SQLite to store details about private gems. The database will be located in ~/.gemstash, however you won’t see the database appear until you start using private gems. If you prefer, you can use a different database.

Gemstash temporarily caches things like gem dependencies in memory. Anything cached in memory will last for 30 minutes before being retrieved again. You can use memcached instead of caching in memory. Gem files are always cached permanently, so bundling with a Gemfile.lock with all gems cached will never call out to

The server you ran is provided via Puma and Rack, however they are not customizable at this point.

Deep Dive

Deep dive into more subjects:


An anatomy of various configuration and commands:

To see what has changed in recent versions of Gemstash, see the CHANGELOG.


After checking out the repo, run bin/setup to install dependencies. Then, run rake to run RuboCop and the tests. While developing, you can run bin/gemstash to run Gemstash. You can also run bin/console for an interactive prompt that will allow you to experiment.


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


The gem is available as open source under the terms of the MIT License.


A cache and private gem server




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