Another 20MB could be removed

[030]

What about running the RUN commands in one layer instead of three, see https://devops.stackexchange.com/a/417/210

https://github.com/tianon/docker-brew-ubuntu-core/blob/5a80061eeed1a4c395066d922bf7f1a0ea79e73c/bionic/Dockerfile

This will save another 20MB according to docker-dive.

[● Layers]─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Cmp   Size  Command
    102 MB  FROM sha256:604cbde1
     745 B  set -xe   && echo '#!/bin/sh' > /usr/sbin/policy-rc.d  && echo 'exit 101' >> /usr/sbin/policy-rc.d  && chmod +x /usr/sbin/p
       0 B  rm -rf /var/lib/apt/lists/*
       7 B  mkdir -p /run/systemd && echo 'docker' > /run/systemd/container
    107 MB  #(nop) COPY dir:b6a97e3dcbfe0203a201aa5e7df785baf454a2e18887f646908dd745d8e236a9 in /opt/jre
    9.1 MB  #(nop) COPY dir:e97b9defdb1d20da0a2b370c5c9a7a1141788b290044b76bd8a9358ac4f31238 in /opt/tomcat

[Layer Details]────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

Digest: sha256:604cbde1a4c8fee1b102f8b64d4f41e62d770b5f8a6b06fb809cfd873a2643c3
Command:
#(nop) ADD file:7ce84f13f11609a50ece7823578159412e2299c812746d1d1f1ed5db0728bd37 in /

[Image Details]────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

Total Image size: 218 MB
Potential wasted space: 20 MB
Image efficiency score: 90 %

Count   Total Space  Path
    2        6.2 MB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic_main_binary-amd64_Packages
    2        4.0 MB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic-updates_main_binary-amd64_Packages
    2        3.2 MB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic_main_i18n_Translation-en
    2        2.4 MB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic-updates_main_i18n_Translation-en
    2        2.2 MB  /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_bionic-security_main_binary-amd64_Packages
    2        1.6 MB  /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_bionic-security_main_i18n_Translation-en
    2        242 kB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic_InRelease
    2         94 kB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic_restricted_binary-amd64_Packages
    2         89 kB  /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_bionic-security_InRelease
    2         89 kB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic-updates_InRelease
    2         82 kB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic-updates_restricted_binary-amd64_Packages
    2         34 kB  /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_bionic-security_restricted_binary-amd64_Packages
    2         17 kB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic_restricted_i18n_Translation-en
    2         12 kB  /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_bionic-updates_restricted_i18n_Translation-en
    2        6.9 kB  /var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_bionic-security_restricted_i18n_Translation-en
    2         234 B  /var/lib/dpkg/diversions
    2           0 B  /var/lib/apt/lists/auxfiles
    2           0 B  /var/lib/apt/lists/lock
    2           0 B  /var/lib/apt/lists/partial

[030]

I have built two images. The first one with the multiple RUN statements and the second with the concatenated RUN. The outcome seems to be the same. I think that a multistage build will reduce the size of the docker image.

[tianon]

Duplicate of #90

[030]

Ok docker-library/official-images#3383