Create a base image

So you want to create your own Base Image? Great!

The specific process will depend heavily on the Linux distribution you want to package. We have some examples below, and you are encouraged to submit pull requests to contribute new ones.

Create a full image using tar

In general, you’ll want to start with a working machine that is running the distribution you’d like to package as a base image, though that is not required for some tools like Debian’s Debootstrap, which you can also use to build Ubuntu images.

It can be as simple as this to create an Ubuntu base image:

$ sudo debootstrap raring raring > /dev/null
$ sudo tar -C raring -c . | docker import - raring

a29c15f1bf7a

$ docker run raring cat /etc/lsb-release

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=13.04
DISTRIB_CODENAME=raring
DISTRIB_DESCRIPTION="Ubuntu 13.04"

There are more example scripts for creating base images in the Docker GitHub Repo:

• BusyBox
• CentOS / Scientific Linux CERN (SLC) on Debian/Ubuntu or on CentOS/RHEL/SLC/etc.
• Debian / Ubuntu

Creating a simple base image using scratch

You can use Docker’s reserved, minimal image, scratch, as a starting point for building containers. Using the scratch “image” signals to the build process that you want the next command in the Dockerfile to be the first filesystem layer in your image.

While scratch appears in Docker’s repository on the hub, you can’t pull it, run it, or tag any image with the name scratch. Instead, you can refer to it in your Dockerfile. For example, to create a minimal container using scratch:

FROM scratch
ADD hello /
CMD ["/hello"]

Assuming you built the “hello” executable example from the Docker GitHub example C-source code, and you compiled it with the -static flag, you can then build this Docker image using: docker build --tag hello .

NOTE: Because Docker for Mac and Docker for Windows use a Linux VM, you must compile this code using a Linux toolchain to end up with a Linux binary. Not to worry, you can quickly pull down a Linux image and a build environment and build within it:

$ docker run --rm -it -v $PWD:/build ubuntu:16.04
container# apt-get update && apt-get install build-essential
container# cd /build
container# gcc -o hello -static -nostartfiles hello.c

Then you can run it (on Linux, Mac, or Windows) using: docker run --rm hello

This example creates the hello-world image used in the tutorials. If you want to test it out, you can clone the image repo.

More resources

There are lots more resources available to help you write your Dockerfile.

• There’s a complete guide to all the instructions available for use in a Dockerfile in the reference section.
• To help you write a clear, readable, maintainable Dockerfile, we’ve also written a Dockerfile best practices guide.
• If your goal is to create a new Official Repository, be sure to read up on Docker’s Official Repositories.