How to reduce docker image size of wildfly application - docker

Question

We are having a docker image whose size is around 858 MB. We want to reduce it's size.
Out of 858 MB
APP Size: 352 MB (EAR FILE)
WILDFLY (18.0.1): 212 MB
adoptopenjdk:11: 123 MB
USR DIR : 116 MB
Is there any way to reduce size?
First Dockerfile --wildfly-11.8:latest
FROM adoptopenjdk/openjdk11:jre-11.0.6_10-alpine
ENV WILDFLY_VERSION 18.0.1.Final
ENV WILDFLY_SHA1 ef0372589a0f08c53e7291721a7e3f7d9
ENV MODULES_FILENAME modules.tar
ENV MODULES_SHA1 2dcfee4045b7d026d7d6290cebc772482
ENV JBOSS_HOME /opt/wildfly
RUN useradd -ms /bin/bash jboss
RUN cd $HOME \
&& curl -O -k https://download.jboss.org/wildfly/$WILDFLY_VERSION/wildfly-$WILDFLY_VERSION.tar.gz \
&& sha1sum wildfly-$WILDFLY_VERSION.tar.gz | grep $WILDFLY_SHA1 \
&& tar xf wildfly-$WILDFLY_VERSION.tar.gz \
&& mv $HOME/wildfly-$WILDFLY_VERSION $JBOSS_HOME \
&& rm wildfly-$WILDFLY_VERSION.tar.gz \
&& chown -R jboss:0 ${JBOSS_HOME} \
&& chmod -R g+rw ${JBOSS_HOME} \
&& curl -p ftp://ftp.co.il//wildfly/1801/$MODULES_FILENAME --user "app:qax" --ftp-create-dirs -O \
&& sha1sum $MODULES_FILENAME | grep $MODULES_SHA1 \
&& tar xf ${MODULES_FILENAME} \
&& rm ${MODULES_FILENAME} \
&& cp -r ./* ${JBOSS_HOME} \
&& rm -rf ./*
COPY configuration /opt/wildfly/standalone/configuration
COPY standalone.conf /opt/wildfly/bin
USER jboss
EXPOSE 8080
CMD cd /opt/wildfly/bin && ./standalone.sh -b="0.0.0.0" -c=$STANDALONE_CONFIG
Second Dockerfile
FROM wildfly-11.8:latest
ENV DEPLOYMENT_LOCATION /opt/wildfly/standalone/deployments
ARG ear_file_path
COPY $ear_file_path $DEPLOYMENT_LOCATION

Answer 1

There are many ways to reduce the size of a Docker image.
1. Use an alpine image or minimum sized one as the base image.
For an official Docker image in the Docker hub, there will be different tags for a single repository. Example: ubuntu:stable, ubuntu:latest, ubuntu:alpine, where alpine would consume the least size.
2. Use Multi Staged Dockerfile.
When writing a Dockerfile, split the requirement into sections.
Like:
(a) If you need to copy the files to the work directory first, do them in the first stage.
(b) Next if you require to install packages, do that in the next stage.
(c) And, finally you need to expose a port and run some commands, do that in the last and final stage.
Example dockerfile:
# Use an official Ubuntu runtime as a base image.
FROM ubuntu:latest AS base
#To create working directory.
WORKDIR /application
# To add contents to the working directory.
ADD . /application
# Use the base image to create a packaged image.
FROM base AS package
#To create add to the existing working directory.
WORKDIR /application
# To install necessary packages.
RUN apt update \
&& apt install nginx -y
&& apt install docker -y
# Use the packaged image to create a final image.
FROM package AS final
#To create add to the existing working directory.
WORKDIR /application
# To Run Commands after the container is run.
CMD ["echo", "Hello world"]
This way, you can reduce the size of the Docker image thats created.
Refer: https://docs.docker.com/develop/develop-images/multistage-build/
Thanks.