Add an ONBUILD instruction to a dockerfile

Adds an ONBUILD instruction to register trigger instructions to be executed later, when the image is used as the base for another build.

Usage

dfi_onbuild(dockerfile, instruction)

Arguments

dockerfile

A dockerfile object

instruction

Instruction to run on build (without the instruction name)

Value

An updated dockerfile object with the ONBUILD instruction added

Details

The ONBUILD instruction registers a trigger instruction that will be executed when the image is used as the base for another build. The trigger is executed in the context of the downstream build, as if it had been inserted immediately after the FROM instruction in the downstream Dockerfile.

This is useful for creating "builder" images that can set up a common build environment for applications.

Note: ONBUILD instructions are not inherited by "grand-children" builds.

See also

dfi_from() for specifying the base image & Official Docker ONBUILD documentation

Other dockerfile instruction functions: dfi_add(), dfi_arg(), dfi_cmd(), dfi_copy(), dfi_entrypoint(), dfi_env(), dfi_expose(), dfi_from(), dfi_healthcheck(), dfi_label(), dfi_maintainer(), dfi_run(), dfi_shell(), dfi_stopsignal(), dfi_user(), dfi_volume(), dfi_workdir()

Examples

# Add ONBUILD triggers for package installation
df <- dockerfile() |>
  dfi_from("rocker/r-ver:4.4.0") |>
  dfi_onbuild("COPY renv.lock /app/renv.lock") |>
  dfi_onbuild("RUN R -e \"renv::restore()\"")
df
#> FROM rocker/r-ver:4.4.0
#> ONBUILD COPY renv.lock /app/renv.lock
#> ONBUILD RUN R -e "renv::restore()"