Demo Build Tomcat image

In this tutorial, you’ll learn how to create a Docker image for Apache Tomcat on a CentOS 7 base. We’ll introduce a build-time argument (ARG) for Tomcat versioning, and demonstrate how to override it at build time.

Table of Contents

• Prerequisites
• Clone the Repository
• Reviewing the Dockerfile
• Dockerfile Instruction Reference
• Building and Running the Default Image
• Building with a Custom Tomcat Version
• Links and References

Prerequisites

• Docker Engine installed (≥ 19.03)
• Basic familiarity with Docker commands
• Internet access to download Tomcat and sample WAR

Clone the Repository

Get the sample project containing our Dockerfile:

cd /tmp
git clone https://github.com/yogeshraheja/dockertomcat.git
cd dockertomcat
ls -ltr
# README.md  Dockerfile

Reviewing the Dockerfile

Below is the complete Dockerfile. It installs OpenJDK 8, downloads Tomcat into /opt/tomcat, sets permissions, and deploys a sample WAR file.

FROM centos:7

# Define a build-time variable for Tomcat version
ARG tomcat_version=8.5.6

# Install prerequisites
RUN yum install -y epel-release java-1.8.0-openjdk.x86_64 wget

# Create tomcat group and home directory
RUN groupadd tomcat && mkdir -p /opt/tomcat

# Create non-interactive tomcat user
RUN useradd -s /bin/nologin -g tomcat -d /opt/tomcat tomcat

# Download and extract Tomcat
WORKDIR /
RUN wget https://archive.apache.org/dist/tomcat/tomcat-8/v${tomcat_version}/bin/apache-tomcat-${tomcat_version}.tar.gz \
 && tar -zxvf apache-tomcat-${tomcat_version}.tar.gz -C /opt/tomcat --strip-components=1

# Set ownership and permissions
RUN cd /opt/tomcat \
 && chgrp -R tomcat conf bin lib logs temp webapps work \
 && chmod g+rx conf \
 && chmod g+r conf/* \
 && chown -R tomcat tomcat logs temp webapps work \
 && chmod g+r bin/*

# Deploy sample application
WORKDIR /opt/tomcat/webapps
RUN wget https://tomcat.apache.org/tomcat-7.0-doc/appdev/sample/sample.war

# Expose port and define startup command
EXPOSE 8080
CMD ["/opt/tomcat/bin/catalina.sh","run"]

Dockerfile Instruction Reference

Building and Running the Default Image

Build with the default Tomcat version (8.5.6):

docker build -t yogeshraheja/tomcatone:v1 .

Expected output:

Successfully built <IMAGE_ID>
Successfully tagged yogeshraheja/tomcatone:v1

Run the container, mapping host port 84 to container port 8080:

docker run -d --name tomcat_default -p 84:8080 yogeshraheja/tomcatone:v1

Now visit http://<host>:84 in your browser. You should see the Tomcat welcome page for version 8.5.6.

Building with a Custom Tomcat Version

You can override tomcat_version at build time to use any release from the Apache Tomcat Archive:

docker build \
  --build-arg tomcat_version=8.5.8 \
  -t yogeshraheja/tomcatone:v2 .

Sample output:

Successfully built <NEW_IMAGE_ID>
Successfully tagged yogeshraheja/tomcatone:v2

Verify both images:

docker image ls yogeshraheja/tomcatone
# REPOSITORY             TAG    IMAGE ID       SIZE
# yogeshraheja/tomcatone  v2     <NEW_IMAGE_ID> 497MB
# yogeshraheja/tomcatone  v1     <OLD_IMAGE_ID> 497MB

Run the new container on port 86:

docker run -d --name tomcat_custom -p 86:8080 yogeshraheja/tomcatone:v2

Now open http://<host>:86 to confirm you’re running Tomcat version 8.5.8.

Links and References

• Dockerfile Reference
• Apache Tomcat Archive
• Docker Documentation
• GitHub: dockertomcat