rename '21' folder to 'preview'

alpine/preview/Dockerfile

@@ -0,0 +1,93 @@
+ARG ALPINE_TAG=3.18.4
+FROM alpine:"${ALPINE_TAG}" AS jre-build
+ARG JAVA_VERSION
+ARG TARGETPLATFORM
+
+# hadolint ignore=DL4006
+RUN apk add --no-cache jq wget \
+  && BUILD_NUMBER=$(echo $JAVA_VERSION | cut -d'+' -f2) \
+  && JAVA_MAJOR_VERSION=$(echo $JAVA_VERSION | cut -d'+' -f1) \
+  && JAVA_VERSION_ENCODED=$(echo $JAVA_VERSION | jq '@uri' -jRr) \
+  && CONVERTED_ARCH=$(arch | sed 's/x86_64/x64/') \
+  && wget --quiet https://github.com/adoptium/temurin"${JAVA_MAJOR_VERSION}"-binaries/releases/download/jdk-"${JAVA_VERSION_ENCODED}"-ea-beta/OpenJDK"${JAVA_MAJOR_VERSION}"U-jdk_"${CONVERTED_ARCH}"_alpine-linux_hotspot_ea_"${JAVA_MAJOR_VERSION}"-0-"${BUILD_NUMBER}".tar.gz -O /tmp/jdk.tar.gz \
+  && tar -xzf /tmp/jdk.tar.gz -C /opt/ \
+  && rm -f /tmp/jdk.tar.gz
+
+ENV PATH=/opt/jdk-${JAVA_VERSION}/bin:$PATH
+
+# Generate smaller java runtime without unneeded files
+# for now we include the full module path to maintain compatibility
+# while still saving space (approx 200mb from the full distribution)
+RUN if [ "$TARGETPLATFORM" != 'linux/arm/v7' ]; then \
+    case "$(jlink --version 2>&1)" in \
+      # jlink version 11 has less features than JDK17+
+      "11."*) strip_java_debug_flags="--strip-debug" ;; \
+      *) strip_java_debug_flags="--strip-java-debug-attributes" ;; \
+    esac; \
+    jlink \
+      --add-modules ALL-MODULE-PATH \
+      "$strip_java_debug_flags" \
+      --no-man-pages \
+      --no-header-files \
+      --compress=zip-6 \
+      --output /javaruntime; \
+  else \
+    cp -r /opt/jdk-${JAVA_VERSION} /javaruntime; \
+  fi
+
+FROM alpine:"${ALPINE_TAG}" AS build
+
+ARG user=jenkins
+ARG group=jenkins
+ARG uid=1000
+ARG gid=1000
+
+RUN addgroup -g "${gid}" "${group}" \
+  && adduser -h /home/"${user}" -u "${uid}" -G "${group}" -D "${user}"
+
+ARG AGENT_WORKDIR=/home/"${user}"/agent
+
+ENV LANG='en_US.UTF-8' LANGUAGE='en_US:en' LC_ALL='en_US.UTF-8'
+ENV TZ=Etc/UTC
+
+## Always use the latest Alpine packages: no need for versions
+# hadolint ignore=DL3018
+RUN apk add --no-cache \
+      curl \
+      bash \
+      git \
+      git-lfs \
+      musl-locales \
+      openssh-client \
+      openssl \
+      procps \
+      tzdata \
+      tzdata-utils \
+    && rm -rf /tmp/*.apk /tmp/gcc /tmp/gcc-libs.tar* /tmp/libz /tmp/libz.tar.xz /var/cache/apk/*
+
+ARG VERSION=3148.v532a_7e715ee3
+ADD --chown="${user}":"${group}" "https://repo.jenkins-ci.org/public/org/jenkins-ci/main/remoting/${VERSION}/remoting-${VERSION}.jar" /usr/share/jenkins/agent.jar
+RUN chmod 0644 /usr/share/jenkins/agent.jar \
+  && ln -sf /usr/share/jenkins/agent.jar /usr/share/jenkins/slave.jar
+
+
+ENV JAVA_HOME=/opt/java/openjdk
+COPY --from=jre-build /javaruntime "$JAVA_HOME"
+ENV PATH="${JAVA_HOME}/bin:${PATH}"
+
+USER "${user}"
+ENV AGENT_WORKDIR="${AGENT_WORKDIR}"
+RUN mkdir /home/"${user}"/.jenkins && mkdir -p "${AGENT_WORKDIR}"
+
+VOLUME /home/"${user}"/.jenkins
+VOLUME "${AGENT_WORKDIR}"
+WORKDIR /home/"${user}"
+ENV user=${user}
+LABEL \
+    org.opencontainers.image.vendor="Jenkins project" \
+    org.opencontainers.image.title="Official Jenkins Agent Base Docker image" \
+    org.opencontainers.image.description="This is a base image, which provides the Jenkins agent executable (agent.jar)" \
+    org.opencontainers.image.version="${VERSION}" \
+    org.opencontainers.image.url="https://www.jenkins.io/" \
+    org.opencontainers.image.source="https://github.com/jenkinsci/docker-agent" \
+    org.opencontainers.image.licenses="MIT"