Decreasing Docker image size by cleaning yum cache?

[JulianHn]

Hey,

inspired by the discussion here ome/omero-web-docker#67, I checked the Dockerfile for the OMERO.server Docker as well and it is possible to decrease the image size significantly by cleaning the yum caches after installing.

Docker diff:

--- a/Dockerfile
+++ b/Dockerfile
@@ -9,15 +9,20 @@ WORKDIR /opt/setup
 ADD playbook.yml requirements.yml /opt/setup/
 
 RUN yum -y install epel-release \
     && yum -y install ansible sudo ca-certificates \
-    && ansible-galaxy install -p /opt/setup/roles -r requirements.yml
+    && ansible-galaxy install -p /opt/setup/roles -r requirements.yml \
+    && yum -y clean all \
+    && rm -fr /var/cache
 
 ARG OMERO_VERSION=5.6.4
 ARG OMEGO_ADDITIONAL_ARGS=
 ENV OMERODIR=/opt/omero/server/OMERO.server/
 RUN ansible-playbook playbook.yml \
     -e omero_server_release=$OMERO_VERSION \
-    -e omero_server_omego_additional_args="$OMEGO_ADDITIONAL_ARGS"
+    -e omero_server_omego_additional_args="$OMEGO_ADDITIONAL_ARGS" \
+    && yum -y clean all \
+    && rm -fr /var/cache
 
 RUN curl -L -o /usr/local/bin/dumb-init \
     https://github.com/Yelp/dumb-init/releases/download/v1.2.2/dumb-init_1.2.2_amd64 && \

This leads to the following image sizes (updated has an additional yum update -y in the first RUN command.

| Options | Image Size |
| Current | 2.34 GB |
| Cleaned | 1.63 GB |
| Cleaned & Update | 1.73 GB |

This would be a 700MB or almost 30% decrease in image size or roughly 25% if the base CentOS image is updated during the build.

// Julian

[joshmoore]

👍 @JulianHn: thanks for looking into that. Do you want to open a PR?

[JulianHn]

@joshmoore Sure. What is the verdict on performing a yum update?

[joshmoore]

As in ome/omero-web-docker#67 (comment), I'd tend to favor an automated rebuild in order to keep the relationship to upstream images rather than creating our open "custom" centos distribution. Open to other opinions (including the opinion that it will take to long to get the rebuild in place and that we should therefore use yum update as a stop-gap)

[JulianHn]

Implemented into the codebase with #69.