Allow Docker to cache RUN results

Question

I have these commands in a Dockerfile:

RUN apt-get -y update                                #1
RUN apt-get -y install sudo                          #2
RUN sudo apt-get -y update                           #3
RUN sudo apt-get -y upgrade                          #4
RUN sudo apt-get install -y sqlite3 libsqlite3-dev   #5

It looks as though Docker cannot cache line #3 or #4

Is there a way I can allow Docker to cache those results somehow? It's taking a minute or two to update/upgrade every time the image is built and I'd like to reduce this delay.

Answer 1

First thing You should avoid RUN apt-get upgrade or dist-upgrade, as many of the “essential” packages from the base images won't upgrade inside an unprivileged container. If a package contained in the base image is out-of-date, you should contact its maintainers.

I think you need to run apt-get update only once within the Dockerfile & Always combine RUN apt-get update with apt-get install in the same RUN statement like

 RUN apt-get update && apt-get install -y \
    sudo \
    sqlite3 \
    libsqlite3-dev