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DL3059
RUN command_creating_big_files # big files stored in image layer!
RUN command_deleting_these_filesor
RUN command_updating_package_info # cached in image layer and not fresh!
RUN command_using_package_infoRUN command_creating_big_files \
&& command_deleting_these_filesor, respectively
RUN command_updating_package_info \
&& command_using_package_infoEach RUN instruction will create a new layer in the resulting image. Therefore consolidating consecutive RUN instructions will reduce the layer count. This will reduce the size of the image if it allows temporary files to be deleted in the same RUN instruction as the one that created them (see https://docs.docker.com/develop/dev-best-practices/).
In addition to that, each RUN runs in its own shell, which can be the source of confusion when part of a RUN instruction changes something about the environment, because these changes may vanish in the next RUN instruction.
Please review Docker's layer caching. In general you want layers first which don't change often, so they can be cached. Putting easy cacheable and non-cacheable commands in the same layer (by using one RUN command) might have negative performance issues. You might want to ignore this info level rule.