Maintaining multiple docker images with common intermediate/final steps

user_474349 0
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I'm in the situation where I have a bunch of images which come from different sources, but I need to apply the same steps to them. Basically it looks like this:

# dockerfile 1
FROM source1
RUN foo

# dockerfile 2
FROM source2
RUN bar

# dockerfile 3
FROM source3
RUN baz

Given these images, I need to apply some common steps, eg copy certificates, install commonly-used packages, set environment variables, etc.

ENV http_proxy http://proxy-server-address
ENV https_proxy http://proxy-server-address

ADD certs/* /usr/local/share/ca-certificates/

RUN apt install something -y
RUN pip install something-else
# etc

Is there a good way to do this for all the images, without duplicating all the steps into each dockerfile? That would be a maintenance headache, since every time I change a step, I have to make sure I do it for all the files.

dockerfile docker
2 Answers

yes

you can create a shared Dockerfile and take the source image as a build argument

ARG BASE_IMAGE
FROM ${BASE_IMAGE}
# common steps

you can then call it for everyone of your builds with

docker build ... --build-args BASE_IMAGE=<img_name>

EDIT:

this means you call docker build twice for each image

once with the different dockerfiles foo, bar, baz and you should tag it as foo_intermediate etc

and then with the common dockerfile were the base image is foo_intermediate and tag it the way you need e.g. foo

user_60872480

Best practice in this case is creating Dockerfile for base image where you put all the common steps.

In specific Dockerfiles you extend base image using FROM base and put image specific directives.

See sample base image Dockerfile here and specific image Dockerfile extending it here.

user_12643040
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