Supported tags and respective
Where to file issues:
the Docker Community
Supported Docker versions:
the latest release (down to 1.6 on a best-effort basis)
What is Ruby?
Ruby is a dynamic, reflective, object-oriented, general-purpose, open-source programming language. According to its authors, Ruby was influenced by Perl, Smalltalk, Eiffel, Ada, and Lisp. It supports multiple programming paradigms, including functional, object-oriented, and imperative. It also has a dynamic type system and automatic memory management.
How to use this image
Dockerfile in your Ruby app project
FROM ruby:2.5 # throw errors if Gemfile has been modified since Gemfile.lock RUN bundle config --global frozen 1 WORKDIR /usr/src/app COPY Gemfile Gemfile.lock ./ RUN bundle install COPY . . CMD ["./your-daemon-or-script.rb"]
Put this file in the root of your app, next to the
You can then build and run the Ruby image:
$ docker build -t my-ruby-app . $ docker run -it --name my-running-script my-ruby-app
The above example
Dockerfile expects a
Gemfile.lock in your app directory. This
docker run will help you generate one. Run it in the root of your app, next to the
$ docker run --rm -v "$PWD":/usr/src/app -w /usr/src/app ruby:2.5 bundle install
Run a single Ruby script
For many simple, single file projects, you may find it inconvenient to write a complete
Dockerfile. In such cases, you can run a Ruby script by using the Ruby Docker image directly:
$ docker run -it --rm --name my-running-script -v "$PWD":/usr/src/myapp -w /usr/src/myapp ruby:2.5 ruby your-daemon-or-script.rb
By default, Ruby inherits the locale of the environment in which it is run. For most users running Ruby on their desktop systems, that means it's likely using some variation of
en_US.UTF-8, etc). In Docker however, the default locale is
C, which can have unexpected results. If your application needs to interact with UTF-8, it is recommended that you explicitly adjust the locale of your image/container via
-e LANG=C.UTF-8 or
ENV LANG C.UTF-8.
This image sets several environment variables which change the behavior of Bundler and Gem for running a single application within a container (especially in such a way that the development sources of the application can be bind-mounted inside a container and not have
.bundle from the host interfere with the proper functionality of the container).
The environment variables we set are canonically listed in the above-linked
Dockerfiles, but some of them include
If these cause issues for your use case (running multiple Ruby applications in a single container, for example), setting them to the empty string should be sufficient for undoing their behavior.
ruby images come in many flavors, each designed for a specific use case.
This is the defacto image. If you are unsure about what your needs are, you probably want to use this one. It is designed to be used both as a throw away container (mount your source code and start the container to start your app), as well as the base to build other images off of. This tag is based off of
buildpack-deps is designed for the average user of docker who has many images on their system. It, by design, has a large number of extremely common Debian packages. This reduces the number of packages that images that derive from it need to install, thus reducing the overall size of all images on your system.
This image does not contain the common packages contained in the default tag and only contains the minimal packages needed to run
ruby. Unless you are working in an environment where only the
ruby image will be deployed and you have space constraints, we highly recommend using the default image of this repository.
This image is based on the popular Alpine Linux project, available in the
alpine official image. Alpine Linux is much smaller than most distribution base images (~5MB), and thus leads to much slimmer images in general.
This variant is highly recommended when final image size being as small as possible is desired. The main caveat to note is that it does use musl libc instead of glibc and friends, so certain software might run into issues depending on the depth of their libc requirements. However, most software doesn't have an issue with this, so this variant is usually a very safe choice. See this Hacker News comment thread for more discussion of the issues that might arise and some pro/con comparisons of using Alpine-based images.
To minimize image size, it's uncommon for additional related tools (such as
bash) to be included in Alpine-based images. Using this image as a base, add the things you need in your own Dockerfile (see the
alpine image description for examples of how to install packages if you are unfamiliar).
ONBUILD image variants are deprecated, and their usage is discouraged. For more details, see docker-library/official-images#2076.
onbuild variant is really useful for "getting off the ground running" (zero to Dockerized in a short period of time), it's not recommended for long-term usage within a project due to the lack of control over when the
ONBUILD triggers fire (see also
Once you've got a handle on how your project functions within Docker, you'll probably want to adjust your
Dockerfile to inherit from a non-
onbuild variant and copy the commands from the
Dockerfile (moving the
ONBUILD lines to the end and removing the
ONBUILD keywords) into your own file so that you have tighter control over them and more transparency for yourself and others looking at your
Dockerfile as to what it does. This also makes it easier to add additional requirements as time goes on (such as installing more packages before performing the previously-
View license information for the software contained in this image.
As with all Docker images, these likely also contain other software which may be under other licenses (such as Bash, etc from the base distribution, along with any direct or indirect dependencies of the primary software being contained).
Some additional license information which was able to be auto-detected might be found in the
As for any pre-built image usage, it is the image user's responsibility to ensure that any use of this image complies with any relevant licenses for all software contained within.