Distroless Deployments - In Progress

 

“Distroless” images contain only your application and its runtime dependencies. They do not contain package managers, shells or any other programs you would expect to find in a standard Linux distribution.

A distroless image is a slimmed down Linux distribution image plus the application runtime, resulting in the minimum set of binary dependencies required for the application to run.

You don't have Shell in Distroless distribution.

A typical container consists of:

• Distro base layer - linux distribution files (Ubuntu, CentOS, Debian)
• Runtime layer (JRE for Java, Python runtime, glibc for C++)
• Application layer - actual application binaries 

Why should I use distroless images?

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Distroless images are very small. The smallest distroless image, gcr.io/distroless/static-debian11, is around 2 MiB. That's about 50% of the size of alpine (~5 MiB), and less than 2% of the size of debian (124 MiB).

The general syntax involves adding FROM additional times within your Dockerfile - whichever is the last FROM statement is the final base image. To copy artifacts and outputs from intermediate images use COPY --from=<base_image_number>.

https://github.com/GoogleContainerTools/distroless/blob/main/examples/java/Dockerfile

javac HelloJava.java

jar cfe main.jar HelloJava HelloJava.class

java -jar main.jar

FROM openjdk:11-jdk-slim-bullseye AS build-env

COPY HelloJava.java /app

WORKDIR /app

RUN javac HelloJava.java

RUN jar cfe main.jar HelloJava HelloJava.class

FROM gcr.io/distroless/java11-debian11

COPY --from=build-env /app /app

WORKDIR /app

CMD ["main.jar"]

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FROM openjdk:11-jdk-slim-bullseye AS build-env

COPY . /app/examples

WORKDIR /app

RUN javac examples/*.java

RUN jar cfe main.jar examples.HelloJava examples/*.class 

FROM gcr.io/distroless/java11-debian11

COPY --from=build-env /app /app

WORKDIR /app

CMD ["main.jar"]

==================

package examples;

public class HelloJava {

    public static void main(String[] args) {

        System.out.println("Hello world");

    }

}

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