build¶
Performs a docker build, using a Dockerfile to build the application and tags the resulting image. By following the conventions no additional flags are needed, but the following flags are available:
| Flag | Description |
|---|---|
--file,-f <path to Dockerfile> | Used to override the default Dockerfile location (which is $PWD) |
--no-login | Disables login to docker registry (good for local testing) |
--no-pull | Disables pulling of remote images if they already exist (good for local testing) |
--build-arg key=value | Additional Docker build-arg |
--platform value | Specify target architecture architecture. should be a single string for example --platform linux/amd64 |
$ build --file docker/Dockerfile.build --skip-login --build-arg AUTH_TOKEN=abc
Build-args¶
The following build-arg are automatically made available:
| Arg | Value |
|---|---|
CI_COMMIT | The commit being built as exposed by CI |
CI_BRANCH | The branch being built as exposed by CI |
they can be used in a Dockerfile like:
FROM ubuntu
ARG CI_BRANCH
RUN echo "Building $CI_BRANCH"
Export content from build¶
Buildtools build command support exporting content from the actual docker build process, see Custom build outputs. By specifying a special stage in the Dockerfile and name it export you can use the COPY directive to copy files from the build context to the local machine. The copied files will be placed in a folder exported
Example¶
Consider a Dockerfile like this:
FROM debian as build
RUN echo "text to be copied to localhost" >> /testfile
# -- export stage
FROM scratch as export
# Copies the file /testfile from `build` stage to localhost
COPY --from=build /testfile .
# -- resulting image stage
FROM scratch
# Do other stuff
Let's try it:
$ ls
Dockerfile
$ cat Dockerfile
FROM debian as build
RUN echo "text to be copied to localhost" >> /testfile
# -- export stage
FROM scratch as export
# Copies the file /testfile from `build` stage to localhost
COPY --from=build /testfile .
# -- resulting image stage
FROM scratch
# Do other stuff
$ build
... <build output>
$ ls
Dockerfile exported
$ ls exported
testfile
$ cat exported/testfile
text to be copied to localhost