Found consecutive
RUN commands DOK-W1001
Anti-pattern
Minor
18 hours ago
—
a year old
Multiple consecutive
RUN instructions. Consider consolidation. 1FROM httpd
2
3RUN apt update > /dev/null 2>&1
4RUN apt install -y curl postgresql-client redis ncat mariadb-client > /dev/null 2>&1 5
6COPY ./scripts/ /usr/scripts/
7
Description
Each RUN instruction will create a new layer in the resulting image. Therefore squashing consecutive RUN instructions will reduce the layer count (see https://docs.docker.com/develop/dev-best-practices/).
In addition to that, each RUN instruction 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.
Bad Practice
RUN command1
RUN command2
Exception
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. If you are aware of this, and this is a design decision, you can safely ignore this issue.
Recommended
RUN command1 && \
command2