DL3059.md

Pattern: Use of multiple consecutive RUN

Issue: -

Description

Each RUN instruction will create a new layer in the resulting image. Therefore consolidating consecutive RUN instructions will reduce the layer count (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.

Example of incorrect code:

RUN command1
RUN command2

Example of correct code:

RUN command1 \
 && command2

Drawbacks

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.

Further Reading

• Hadolint - DL3059