UBI 9 minimal Liberty container images with Semeru Runtime Java 21 support

The Universal Base Image 9 Minimal is a stripped down image that uses microdnf as a package manager, which allows for the production of smaller application images. Open Liberty Java 21 UBI 9 minimal images are available starting with the 24.0.0.1 release of Open Liberty. The UBI 9 minimal content may impact some application image builds because of missing functionality. Application image builds can use microdnf to install additional packages as required. Unlike UBI 8, UBI 9 is not FIPS compliant at the time of this publication. Other Open Liberty Java version images will continue to use the UBI 8 standard images (Java 8, Java 11, Java 17).

The high-performance IBM Semeru Runtime now supports Java 21, including the various Java 21 language features, such as Virtual threads, scoped values, record patterns, the latest foreign functions and memory API, and more.

For Java 21, the Open Liberty project now uses UBI 9 minimal images with the Semeru Runtime Java 21 JRE container images. The Semeru Runtime JRE images are considerably smaller than the JDK images. The Liberty Java 21 images provide a very nice reduction in the size of application images due to the use of the UBI 9 minimal image and the Semeru Runtime JRE image. The reduced content of the JRE image might impact some application images because of its reduced functionality.

Liberty InstantOn support for Power and Z (s390x) require the UBI 9 based image. The Liberty Java 21 UBI 9 minimal images can now use Liberty InstantOn to achieve faster application startup on the Power and IBM Z (s390x) process architectures. Liberty InstantOn continues to support the x86-64/AMD64 process architectures with the Liberty container images using Java versions 11, 17 and 21.