Chainguard Image for jre-crac

Minimalist Wolfi-based OpenJDK JRE image with CRaC support. Used for running Java applications.

Chainguard Images are regularly-updated, minimal container images with low-to-zero CVEs.

Download this Image

This image is available on cgr.dev:

docker pull cgr.dev/ORGANIZATION/jre-crac:latest

Be sure to replace the ORGANIZATION placeholder with the name used for your organization's private repository within the Chainguard registry.

CRaC Application Example

This section outlines how you can build and run a Java application leveraging CRaC with the Chainguard JRE CRaC Image.

In this example, we'll be using the SpringBoot PetClinic application, with the docs provided here.

Start by cloning the source code for SpringBoot PetClinic:

git clone https://github.com/spring-projects/spring-petclinic && cd spring-petclinic

Now, edit the pom.xml, and add org.crac as a dep, under the dependencies section:

    <dependency>
      <groupId>org.crac</groupId>
      <artifactId>crac</artifactId>
      <version>1.4.0</version>
    </dependency>

Then create a multistage Dockerfile, copying the program after it has been built to the JRE CRaC image:

FROM cgr.dev/ORGANIZATION/jdk-crac

COPY . /home/build/

RUN ./mvnw package

FROM cgr.dev/ORGANIZATION/jre-crac

COPY --from=0 /home/build/target/spring-petclinic-3.3.0-SNAPSHOT.jar /app/

CMD ["-XX:CRaCMinPid=70000", "-XX:CRaCCheckpointTo=/app/checkpoint", "-jar", "/app/spring-petclinic-3.3.0-SNAPSHOT.jar"]

In this example, we've set a high minimum PID as, by default, the process will run with PID 1. We must set the minimum PID as it will conflict with the PID of the process used for restore later. It's also generally a good practice as lower PIDs are typically allocated for other system processes and they must not clash on restore.

Following that, you can build the image:

docker build -t petclinic .

Note that this example tags the image with petclinic. You can now run the image by referencing this tag, as in the following command:

docker run --privileged -v ./checkpoint:/app/checkpoint --name petclinic-before petclinic

Wait until we see that it has started on port 8080.

Open a new terminal, and take a checkpoint:

docker exec petclinic-before jcmd spring-petclinic JDK.checkpoint

On moving back to the original terminal, you'll see the container has stopped. Let's resume the program from the checkpoint:

docker run --privileged -v ./checkpoint:/app/checkpoint --name petclinic-after petclinic -XX:CRaCRestoreFrom=/app/checkpoint

The program should have successfully restored from the checkpoint!:

2024-10-31T13:29:52.236Z  INFO 70473 --- [Attach Listener] o.s.c.support.DefaultLifecycleProcessor  : Restarting Spring-managed lifecycle beans after JVM restore
2024-10-31T13:29:52.258Z  INFO 70473 --- [Attach Listener] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port 8080 (http) with context path '/'
2024-10-31T13:29:52.268Z  INFO 70473 --- [Attach Listener] o.s.c.support.DefaultLifecycleProcessor  : Spring-managed lifecycle restart completed (restored JVM running for 211 ms)

Differences between our JRE and JRE CRaC images

JRE CRaC includes CRaC CRIU

CRaC CRIU allows you to restore you Java programs using the CRaC API quickly with fewer resources.

JRE CRaC runs as root by default

To facilitate an easier workflow for performing checkpoints/restores, the image runs as root by default. It is not possible to leverage CRaC at runtime as non-root.

If you need to use a non-root user, specify java via the USER directive in the Dockerfile.

JRE CRaC disables rseq

Running with rseq enabled breaks restores leveraging CRaC:

pie: 70001: Error (criu/pie/restorer.c:467): failed sys_rseq(0x7f453767a4a0, 0x20, 0x0, 0x53053053) = -22
pie: 70001: Error (criu/pie/restorer.c:2055): Restorer fail 70001
Error (criu/cr-restore.c:2605): Restoring FAILED

If you need to re-enable rseq, pass GLIBC_TUNABLES=glibc.pthread.rseq=1 to the ENV directive in the Dockerfile.

Contact Support

If you have a Zendesk account (typically set up for you by your Customer Success Manager) you can reach out to Chainguard's Customer Success team through our Zendesk portal.

What are Chainguard Images?

Chainguard Images are a collection of container images designed for security and minimalism.

Many Chainguard Images are distroless; they contain only an open-source application and its runtime dependencies. These images do not even contain a shell or package manager. Chainguard Images are built with Wolfi, our Linux undistro designed to produce container images that meet the requirements of a secure software supply chain.

The main features of Chainguard Images include:

• Minimal design, with no unnecessary software bloat
• Automated nightly builds to ensure Images are completely up-to-date and contain all available security patches
• High quality build-time SBOMs (software bills of materials) attesting the provenance of all artifacts within the Image
• Verifiable signatures provided by Sigstore
• Reproducible builds with Cosign and apko (read more about reproducibility)

-dev Variants

As mentioned previously, Chainguard’s distroless Images have no shell or package manager by default. This is great for security, but sometimes you need these things, especially in builder images. For those cases, most (but not all) Chainguard Images come paired with a -dev variant which does include a shell and package manager.

Although the -dev image variants have similar security features as their distroless versions, such as complete SBOMs and signatures, they feature additional software that is typically not necessary in production environments. The general recommendation is to use the -dev variants only to build the application and then copy all application artifacts into a distroless image, which will result in a final container image that has a minimal attack surface and won’t allow package installations or logins.

That being said, it’s worth noting that -dev variants of Chainguard Images are completely fine to run in production environments. After all, the -dev variants are still more secure than many popular container images based on fully-featured operating systems such as Debian and Ubuntu since they carry less software, follow a more frequent patch cadence, and offer attestations for what they include.

Learn More

To better understand how to work with Chainguard Images, we encourage you to visit Chainguard Academy, our documentation and education platform.