mirror of https://github.com/docker/docs.git
93 lines
4.3 KiB
Markdown
93 lines
4.3 KiB
Markdown
---
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description: How to create base images
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keywords: images, base image, examples
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redirect_from:
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- /engine/articles/baseimages/
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title: Create a base image
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---
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Most Dockerfiles start from a parent image. If you need to completely control
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the contents of your image, you might need to create a base image instead.
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Here's the difference:
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- A [parent image](/reference/glossary.md#parent-image) is the image that your
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image is based on. It refers to the contents of the `FROM` directive in the
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Dockerfile. Each subsequent declaration in the Dockerfile modifies this parent
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image. Most Dockerfiles start from a parent image, rather than a base image.
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However, the terms are sometimes used interchangeably.
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- A [base image](/reference/glossary.md#base-image) either has no `FROM` line
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in its Dockerfile, or has `FROM scratch`.
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This topic shows you several ways to create a base image. The specific process
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will depend heavily on the Linux distribution you want to package. We have some
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examples below, and you are encouraged to submit pull requests to contribute new
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ones.
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## Create a full image using tar
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In general, you'll want to start with a working machine that is running
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the distribution you'd like to package as a parent image, though that is
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not required for some tools like Debian's
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[Debootstrap](https://wiki.debian.org/Debootstrap), which you can also
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use to build Ubuntu images.
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It can be as simple as this to create an Ubuntu parent image:
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$ sudo debootstrap xenial xenial > /dev/null
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$ sudo tar -C xenial -c . | docker import - xenial
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a29c15f1bf7a
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$ docker run xenial cat /etc/lsb-release
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DISTRIB_ID=Ubuntu
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DISTRIB_RELEASE=16.04
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DISTRIB_CODENAME=xenial
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DISTRIB_DESCRIPTION="Ubuntu 16.04 LTS"
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There are more example scripts for creating parent images in the Docker
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GitHub Repo:
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- [BusyBox](https://github.com/moby/moby/blob/master/contrib/mkimage/busybox-static)
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- CentOS / Scientific Linux CERN (SLC) [on Debian/Ubuntu](
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https://github.com/moby/moby/blob/master/contrib/mkimage/rinse) or
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[on CentOS/RHEL/SLC/etc.](
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https://github.com/moby/moby/blob/master/contrib/mkimage-yum.sh)
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- [Debian / Ubuntu](
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https://github.com/moby/moby/blob/master/contrib/mkimage/debootstrap)
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## Creating a simple parent image using scratch
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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.
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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`:
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FROM scratch
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ADD hello /
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CMD ["/hello"]
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Assuming you built the "hello" executable example [from the Docker GitHub example C-source code](https://github.com/docker-library/hello-world/blob/master/hello.c), and you compiled it with the `-static` flag, you can then build this Docker image using: `docker build --tag hello .`
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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:
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$ docker run --rm -it -v $PWD:/build ubuntu:16.04
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container# apt-get update && apt-get install build-essential
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container# cd /build
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container# gcc -o hello -static -nostartfiles hello.c
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Then you can run it (on Linux, Mac, or Windows) using: `docker run --rm hello`
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This example creates the hello-world image used in the tutorials.
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If you want to test it out, you can clone [the image repo](https://github.com/docker-library/hello-world).
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## More resources
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There are lots more resources available to help you write your `Dockerfile`.
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* There's a [complete guide to all the instructions](../../reference/builder.md) available for use in a `Dockerfile` in the reference section.
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* To help you write a clear, readable, maintainable `Dockerfile`, we've also
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written a [`Dockerfile` best practices guide](dockerfile_best-practices.md).
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* If your goal is to create a new Official Repository, be sure to read up on Docker's [Official Repositories](/docker-hub/official_repos/).
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