Dockerfile for Tomcat running as non-root user

Dockerfile-tomcat

FROM eclipse-temurin:11-jdk-jammy

## allow to set a user id and group to match the host user for easy file sharing 
ARG USER_ID=1000

## Tomcat version
ARG TOMCAT_VERSION=9.0.70

ENV SETUP_DIR       "/var/local/tomcat"
ENV USER_ID         ${USER_ID}
ENV TOMCAT_VERSION  ${TOMCAT_VERSION}
ENV TOMCAT_FILENAME "apache-tomcat-${TOMCAT_VERSION}"
ENV CATALINA_HOME   "${SETUP_DIR}/${TOMCAT_FILENAME}"
ENV CATALINA_BASE   "/srv/www/catalina-base"

RUN echo "setup dir: ${SETUP_DIR}" \
    && mkdir -p ${SETUP_DIR} \
    && cd ${SETUP_DIR} \
    \
    ## download Tomcat binaries
    && wget https://dlcdn.apache.org/tomcat/tomcat-9/v${TOMCAT_VERSION}/bin/${TOMCAT_FILENAME}.tar.gz \
    && tar -xvf ${TOMCAT_FILENAME}.tar.gz \
    && cd ${TOMCAT_FILENAME} \
    \
    ## create uid=1000(tomcat) gid=1000(tomcat)
    && useradd --uid ${USER_ID} --user-group --shell /bin/bash tomcat \
    \
    ## set group and group permissions to directories
    && chgrp -R tomcat ${CATALINA_HOME} \
    && chmod -R g+rX ${CATALINA_HOME} \
    && chmod -R g+w "${CATALINA_HOME}/logs" "${CATALINA_HOME}/temp" "${CATALINA_HOME}/work" \
    \
    && export CATALINA_HOME=${CATALINA_HOME} \
    && export CATALINA_BASE=${CATALINA_BASE} \
    \
    ## create catalina-base dir and set group permissions
    && mkdir -p ${CATALINA_BASE} \
    && chgrp -R tomcat ${CATALINA_BASE} \
    && chmod -R g+srwX ${CATALINA_BASE} \
    \
    ## switch to new user and populate catalina-base with default files
    && su tomcat \
    && ${CATALINA_HOME}/bin/makebase.sh ${CATALINA_BASE} \
    \
    ## add default html page
    && echo "Hello Tomcat" > ${CATALINA_BASE}/webapps/ROOT/index.html

WORKDIR ${CATALINA_HOME}

## allow other containers to connect
EXPOSE 8080

ENTRYPOINT [ "bin/catalina.sh", "run" ]