openjdk
OpenJDK Overview
Secure your stack with a hardened OpenJDK image freshly-built by Minimus. Minimus images always include the most up-to-date package version for all packages and dependencies contained in the image.
OpenJDK (Open Java Development Kit) is an open-source implementation of the Java Platform, Standard Edition (Java SE). It is a great default choice for Java projects requiring a Java compiler (javac) and standard Java libraries. See also the Minimus tutorial for Java and Minimus tips for multi-stage builds.
Try It Out
To take the Minimus OpenJDK image for a test run, we will require both OpenJDK and OpenJRE in our Dockerfile to keep the build and runtime environments separate and include only the compiled .class in the final image. Our test will also involve a Java project with a simple program that prints a welcome message.
First, create 2 files in your directory:
- Dockerfile
- MyMinimus.java
Save the following code to your Dockerfile:
# === Build Stage ===
FROM reg.mini.dev/openjdk AS builder
COPY MyMinimus.java /home/build/
WORKDIR /home/build/
RUN javac -d /home/build MyMinimus.java
# === Runtime Stage ===
FROM reg.mini.dev/openjre
COPY --from=0 /home/build/MyMinimus.class /app/
WORKDIR /app/
CMD ["java", "MyMinimus"]Save the following Java script to the file MyMinimus.java. Note that for Java to compile properly, the filename must match the public class name, so be sure to save the file as MyMinimus.java.
class MyMinimus
{
public static void main(String args[])
{
System.out.println("Welcome to MyMinimus!");
}
} Next, build the custom image and run it. Note that the period . specifies the current directory as the build context:
docker build -t minimus-java-app .
docker run minimus-java-appYou should see the greeting Welcome to MyMinimus! in your terminal.
Technical Considerations
The OpenJDK image provided by Minimus is a slim, security-hardened alternative to the public image from eclipse-temurin (since the Docker official image is deprecated). The images are largely interchangeable, with a few differences as noted below.
OpenJDK built by Minimus:
- Runs as non-root by default for a security-first approach that protects against privilege escalation attacks. The public image runs as root.
- The entrypoint is null, while the public image entrypoint script defaults to
/__cacert_entrypoint.sh. The default CMD isjshellin both images. - The default working directory is
/home/build. For the public image, the default working directory is the root directory (/). - Drill down on the version specification tab to see the default user, listening ports, entrypoint, volumes, environment variables, etc.
The Payoff
A hardened, minimal image that will remain more secure for the long run and accrue vulnerabilities at a slower rate.
- See the risk reduction dashboard for a detailed CVE comparison over the past 30 days.
- Review the compliance report to see the default hardening and security configurations for the image.
Terms & Info
Trademark
This catalog is published by Minimus. All product names, logos, and marks, other than those belonging to Minimus, shown are owned by their respective rights holders and appear here only to identify the open source software each image contains. Minimus claims no ownership of those marks and implies no affiliation with, endorsement by, certification by, or sponsorship by any rights holder.
Disclaimer
Images are provided "as-is" without warranty of any kind. "Hardened" refers to the security configuration applied at the time of build and does not constitute a guarantee of ongoing security or absence of vulnerabilities. The free tier is provided without support, SLA, or guaranteed patching timelines. Security updates may be applied to paid subscriptions before or instead of free tier images. By pulling or using any image you agree to our Terms of Use.