Docker in DockerEstimated reading time: 7 minutes
Docker in Docker!
GitHub repo: https://github.com/docker-library/docker
Supported tags and respective
For detailed information about the published artifacts of each of the above supported tags (image metadata, transfer size, etc), please see the
repos/docker directory in the
docker-library/repo-info GitHub repo.
For more information about this image and its history, please see the relevant manifest file (
library/docker). This image is updated via pull requests to the
docker-library/official-images GitHub repo.
What is Docker in Docker?
Although running Docker inside Docker is generally not recommended, there are some legitimate use cases, such as development of Docker itself.
Docker is an open-source project that automates the deployment of applications inside software containers, by providing an additional layer of abstraction and automation of operating-system-level virtualization on Linux, Mac OS and Windows.
Before running Docker-in-Docker, be sure to read through Jérôme Petazzoni’s excellent blog post on the subject, where he outlines some of the pros and cons of doing so (and some nasty gotchas you might run into).
If you are still convinced that you need Docker-in-Docker and not just access to a container’s host Docker server, then read on.
How to use this image
Start a daemon instance
IMPORTANT: this image defaults to
--storage-driver=vfs, which will be very slow and inefficient (but is the only driver which is guaranteed to work regardless of your underlying filesystem). Which driver you should use varies depending on your needs, but a good rule of thumb is that your DinD instance should be using the same driver as your host (which can be seen under
Storage Driver in the output of
docker info). See the “Custom daemon flags” section below for how to specify your storage driver.
$ docker run --privileged --name some-docker -d docker:1.8-dind
--privileged is required for Docker-in-Docker to function properly, but it should be used with care as it provides full access to the host environment, as explained in the relevant section of the Docker documentation.
This image includes
EXPOSE 2375 (the Docker port), so standard container linking will make it automatically available to the linked containers (as the following examples illustrate).
Connect to it from a second container
$ docker run --rm --link some-docker:docker docker:1.7 version Client version: 1.7.1 Client API version: 1.19 Go version (client): go1.4.2 Git commit (client): 786b29d OS/Arch (client): linux/amd64 Server version: 1.8.1 Server API version: 1.20 Go version (server): go1.4.2 Git commit (server): d12ea79 OS/Arch (server): linux/amd64
$ docker run -it --rm --link some-docker:docker docker:1.8 sh / # docker version Client: Version: 1.8.1 API version: 1.20 Go version: go1.4.2 Git commit: d12ea79 Built: Thu Aug 13 02:49:29 UTC 2015 OS/Arch: linux/amd64 Server: Version: 1.8.1 API version: 1.20 Go version: go1.4.2 Git commit: d12ea79 Built: Thu Aug 13 02:49:29 UTC 2015 OS/Arch: linux/amd64
$ docker run --rm --link some-docker:docker docker info Containers: 0 Images: 0 Storage Driver: vfs Execution Driver: native-0.2 Logging Driver: json-file Kernel Version: 4.0.9-gentoo Operating System: Alpine Linux v3.2 (containerized) CPUs: 8 Total Memory: 31.4 GiB Name: 4f19ef15a373 ID: 3GTC:FH6T:4G5U:7NF4:GM77:JGYU:BOKS:XFCY:H3IQ:JDJ5:X73Z:2K2K WARNING: bridge-nf-call-iptables is disabled WARNING: bridge-nf-call-ip6tables is disabled
$ docker run --rm --link some-docker:docker docker:git build https://github.com/docker-library/hello-world.git Sending build context to Docker daemon 132.1 kB Step 0 : FROM scratch ---> Step 1 : COPY hello / ---> 29bef505052d Removing intermediate container f98aab888906 Step 2 : CMD /hello ---> Running in a735b4037032 ---> 3c2b1350a3c4 Removing intermediate container a735b4037032 Successfully built 3c2b1350a3c4
$ docker run --rm -v /var/run/docker.sock:/var/run/docker.sock docker version Client: Version: 1.8.1 API version: 1.20 Go version: go1.4.2 Git commit: d12ea79 Built: Thu Aug 13 02:49:29 UTC 2015 OS/Arch: linux/amd64 Server: Version: 1.9.0-dev API version: 1.21 Go version: go1.4.2 Git commit: 7e3088c-dirty Built: Tue Aug 18 19:53:53 UTC 2015 OS/Arch: linux/amd64
Custom daemon flags
$ docker run --privileged --name some-overlay-docker -d docker:dind --storage-driver=overlay
Where to Store Data
Important note: There are several ways to store data used by applications that run in Docker containers. We encourage users of the
docker images to familiarize themselves with the options available, including:
- Let Docker manage the storage of your data by writing to disk on the host system using its own internal volume management. This is the default and is easy and fairly transparent to the user. The downside is that the files may be hard to locate for tools and applications that run directly on the host system, i.e. outside containers.
- Create a data directory on the host system (outside the container) and mount this to a directory visible from inside the container. This places the files in a known location on the host system, and makes it easy for tools and applications on the host system to access the files. The downside is that the user needs to make sure that the directory exists, and that e.g. directory permissions and other security mechanisms on the host system are set up correctly.
The Docker documentation is a good starting point for understanding the different storage options and variations, and there are multiple blogs and forum postings that discuss and give advice in this area. We will simply show the basic procedure here for the latter option above:
- Create a data directory on a suitable volume on your host system, e.g.
dockercontainer like this:
$ docker run --privileged --name some-docker -v /my/own/var-lib-docker:/var/lib/docker -d docker:dind
-v /my/own/var-lib-docker:/var/lib/docker part of the command mounts the
/my/own/var-lib-docker directory from the underlying host system as
/var/lib/docker inside the container, where Docker by default will write its data files.
View license information for the software contained in this image.
Supported Docker versions
This image is officially supported on Docker version 17.04.0-ce.
Support for older versions (down to 1.6) is provided on a best-effort basis.
Please see the Docker installation documentation for details on how to upgrade your Docker daemon.
If you have any problems with or questions about this image, please contact us through a GitHub issue. If the issue is related to a CVE, please check for a
cve-tracker issue on the
official-images repository first.
You can also reach many of the official image maintainers via the
#docker-library IRC channel on Freenode.
You are invited to contribute new features, fixes, or updates, large or small; we are always thrilled to receive pull requests, and do our best to process them as fast as we can.
Before you start to code, we recommend discussing your plans through a GitHub issue, especially for more ambitious contributions. This gives other contributors a chance to point you in the right direction, give you feedback on your design, and help you find out if someone else is working on the same thing.
Documentation for this image is stored in the
docker/ directory of the
docker-library/docs GitHub repo. Be sure to familiarize yourself with the repository’s
README.md file before attempting a pull request.