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Additional Build Parameters

DOCKERFILE_PATH and DOCKER_BUILD_PATH

DOCKERFILE_PATH defines the path name of the Dockerfile to be used during a build, and DOCKER_BUILD_PATH defines the build directory. Both are relative to the top of the repo directory.

Here, we show how these two parameters work using an example. Supposed we have a project_repo repository on GitHub, where we have Dockerfile and dirname at the top directory and a work subdirectory, as shown below.

$ cd project_repo
$ cat Dockerfile
FROM nginx
ADD dirname .
RUN DIR=`cat dirname` && echo "<html><body><p>build dir at ${DIR}, and Dockerfile at top.</p></body></html>" > /usr/share/nginx/html/index.html

$ cat dirname
top

$ cd work
$ cat Dockerfie
FROM nginx
ADD dirname .
RUN DIR=`cat dirname` && echo "<html><body><p>build dir at ${DIR}, and Dockerfile at work.</p></body></html>" > /usr/share/nginx/html/index.html

$ cat dirname
work

Both Dockerfiles create a nginx Web server container with a modified default page. By accessing the page, we can find which Dockerfile and build directory were used during a build.

The following table shows four combinations of DOCKERFILE_PATH and DOCKER_BUILD_PATH values. As you can see, DOCKERFILE_PATH is always relative to the top of the repo directory even when the build directory is a subdirectory.

DOCKERFILE_PATH DOCKER_BUILD_PATH Text to be shown at nginx default page
"Dockerfile" "" build dir at top, and Dockerfile at top.
"Dockerfile" "work" build dir at work, and Dockerfile at top.
"work/Dockerfile" "" build dir at top, and Dockerfile at work.
"work/Dockerfile" "work" build dir at work, and Dockerfile at work.

Using these two parameters, you can build multiple kinds of container images out of a single GitHub repo. If you want to use a single SBS instance to build those images and to push them to the same container repository, please note the following behavior of SBS.

  • Use a different IMAGE_TAG_PREFIX for a different container built from the same GitHub repo. Otherwise, the same image tag will be assigned to multiple containers, and hence only the image pushed last remains accessible.
  • Make sure to run ./build.py update to update build parameters (e.g. DOCKERFILE_PATH, DOCKER_BUILD_PATH, IMAGE_TAG_PREFIX) inside the SBS instance to build a different container. Your modifications to a config json file won't be effective until you run ./build.py update.